title: Program hangs when using "matplotlib.mlab.griddata"
body: <p>I have written a script (Python 2.6) to grid data in x,y,z (.csv format), and display a contour plot of the data.</p>
  
  <p>The script works for some datasets but not others - even though both datasets were created using the same script.</p>
  
  <p>The datasets to be plotted are created by sub-sampling from a master dataset.</p>
  
  <p>Here is an example of every_4.csv (master dataset sub-sampled for every 4 rows).</p>
  
  <pre><code>Easting Northing    TMI_nT 
  526243.0    5254128.9   62278.8
  526259.4    5254128.9   62352.3
  526275.9    5254128.9   62303.3
  526292.3    5254128.9   62361.9
  526308.8    5254128.9   62667.8
  526325.2    5254128.9   62668.6
  526341.7    5254128.9   61700.1
  526358.1    5254128.9   62029.6
  526374.6    5254128.9   62042.7
  </code></pre>
  
  <p>This data plots correctly using my script.</p>
  
  <p>"every_3.csv" Which is of the same form as every_4.csv causes my script to hang (no error message) when it tries to execute:</p>
  
  <blockquote>
    <p>zi = griddata(x, y, z, xi, yi)</p>
  </blockquote>
  
  <p>here is the script I am using:</p>
  
  <pre><code>### program to test gridding and contouring
  
  import numpy as N
  import scipy as S
  from matplotlib.mlab import griddata
  import matplotlib.pyplot as P
  import matplotlib.cm as CM
  
  longarray = N.loadtxt('every_3.csv', skiprows=1, delimiter=',')
  x = longarray[:,0]
  y = longarray[:,1]
  z = longarray[:,2]
  
  max_x = max(x)
  min_x = min(x)
  max_y = max(y)
  min_y = min(y)
  
  ##print max_y
  ##print min_x
  ##print max_x
  ##print min_y
  
  xi = N.linspace(min_x, max_x)
  yi = N.linspace(min_y, max_y)
  
  zi = griddata(x, y, z, xi, yi)
  print zi
  CS = P.contourf(xi,yi,zi,15,cmap=CM.RdYlBu)
  
  P.show()
  </code></pre>
  
  <p>I cannot work out why this script hangs for some files and not others.</p>
  
  <p>Note:  If I open every_3.csv in excel and delete some rows (say 50% of the rows in the file) I can get the script to run...</p>
  
  <p><strong>Update</strong></p>
  
  <p>Here is a more complete data set:</p>
  
  <pre><code>Easting Northing    TMI_nT
  526243  5254128.9   62278.8
  526247.1    5254128.9   62413.3
  526251.2    5254128.9   62398.6
  526255.3    5254128.9   62355.7
  526259.4    5254128.9   62352.3
  526263.6    5254128.9   62327.8
  526267.7    5254128.9   62279.6
  526271.8    5254128.9   62322.1
  526275.9    5254128.9   62303.3
  526280  5254128.9   62375.1
  526284.1    5254128.9   62561.4
  526288.2    5254128.9   62302.4
  526292.3    5254128.9   62361.9
  526374.6    5254128.9   62042.7
  526378.7    5254128.9   62139.6
  526382.8    5254128.9   61891.5
  526386.9    5254128.9   61937.2
  526391  5254128.9   62238.7
  526395.1    5254128.9   62344.9
  526399.2    5254128.9   62220.4
  526403.3    5254128.9   62027
  526407.4    5254128.9   62392.2
  526411.6    5254128.9   63252.4
  526415.7    5254128.9   62951.8
  526419.8    5254128.9   62504.5
  526423.9    5254128.9   62927.6
  526428  5254128.9   62813.9
  526432.1    5254128.9   63381.4
  526436.2    5254128.9   63458.5
  526440.3    5254128.9   63273
  526444.4    5254128.9   62945
  526448.6    5254128.9   62466.2
  526452.7    5254128.9   62300.3
  526456.8    5254128.9   62164.3
  526460.9    5254128.9   62144.7
  526465  5254128.9   62216.7
  526469.1    5254128.9   62307.3
  526473.2    5254128.9   62437.6
  526477.3    5254128.9   62495
  526481.4    5254128.9   62256.1
  526485.6    5254128.9   61951.2
  526489.7    5254128.9   61632
  526493.8    5254128.9   61221.6
  526497.9    5254128.9   62414.3
  526502  5254128.9   64152.7
  526506.1    5254128.9   61964.7
  526510.2    5254128.9   61952.5
  526514.3    5254128.9   62104.2
  526518.4    5254128.9   62190.4
  526522.6    5254128.9   62334.8
  526526.7    5254128.9   62468.8
  526530.8    5254128.9   62437.3
  526296.4    5253951.8   62138
  526300.6    5253951.8   62283.3
  526304.7    5253951.8   62336
  526308.8    5253951.8   62367.6
  526312.9    5253951.8   62416
  526317  5253951.8   62395.3
  526321.1    5253951.8   62364.1
  526325.2    5253951.8   62363.2
  526329.3    5253951.8   62292.6
  526333.4    5253951.8   62252
  526337.6    5253951.8   62179.1
  526341.7    5253951.8   62086.8
  526345.8    5253951.8   62069.6
  526349.9    5253951.8   62108.4
  526354  5253951.8   61994
  526358.1    5253951.8   61909.1
  526362.2    5253951.8   61943.1
  526366.3    5253951.8   61918.6
  526370.4    5253951.8   61895.9
  526374.6    5253951.8   61871.6
  526378.7    5253951.8   61821.4
  526382.8    5253951.8   61778.1
  526386.9    5253951.8   61738.2
  526391  5253951.8   61644.5
  526395.1    5253951.8   61555.8
  526399.2    5253951.8   61540
  526403.3    5253951.8   61549.6
  526407.4    5253951.8   61596.4
  526411.6    5253951.8   61566.5
  526415.7    5253951.8   61565.1
  526419.8    5253951.8   61287.6
  526423.9    5253951.8   61368
  526428  5253951.8   61481.5
  526432.1    5253951.8   61228.8
  526436.2    5253951.8   61024.6
  526440.3    5253951.8   60960.9
  526444.4    5253951.8   61146.7
  526448.6    5253951.8   61240.8
  526452.7    5253951.8   61396.5
  526456.8    5253951.8   61536.9
  526460.9    5253951.8   61677.1
  526465  5253951.8   61715.6
  526469.1    5253951.8   61749.8
  526473.2    5253951.8   61809.1
  526477.3    5253951.8   61939.2
  526481.4    5253951.8   61913.3
  526485.6    5253951.8   62035.7
  526489.7    5253951.8   62108.9
  526493.8    5253951.8   62025.4
  526497.9    5253951.8   61929.1
  526502  5253951.8   61947.2
  526506.1    5253951.8   62182.8
  526510.2    5253951.8   62239.3
  526514.3    5253951.8   62071.7
  526518.4    5253951.8   62054.5
  526522.6    5253951.8   62001.3
  526526.7    5253951.8   61993.5
  526530.8    5253951.8   62009.3
  526534.9    5253951.8   61966.5
  526539  5253951.8   61947.2
  526543.1    5253951.8   61936.4
  526547.2    5253951.8   61974
  526551.3    5253951.8   62023.6
  526555.4    5253951.8   62068.7
  526559.6    5253951.8   62096.1
  526563.7    5253951.8   62113.4
  526567.8    5253951.8   62085.1
  526571.9    5253951.8   62100.7
  526576  5253951.8   62180.1
  526580.1    5253951.8   62231.8
  526584.2    5253951.8   62142.9
  526588.3    5253951.8   62137.1
  526592.4    5253951.8   62135.4
  526596.6    5253951.8   62118.5
  526600.7    5253951.8   62104.9
  526604.8    5253951.8   62126.5
  526608.9    5253951.8   62129.7
  526613  5253951.8   62127
  526617.1    5253951.8   62122.8
  526621.2    5253951.8   62091.5
  526625.3    5253951.8   62143.7
  526629.4    5253951.8   62144.2
  526633.6    5253951.8   62148.1
  526637.7    5253951.8   62145.6
  526641.8    5253951.8   62247.1
  526645.9    5253951.8   62267.5
  526650  5253951.8   62131.8
  526243  5253955.9   62073.3
  526247.1    5253955.9   62018.5
  526251.2    5253955.9   61948.4
  526255.3    5253955.9   61965.1
  526259.4    5253955.9   61980.3
  526263.6    5253955.9   61982.2
  526267.7    5253955.9   61985.3
  526271.8    5253955.9   61979.6
  526275.9    5253955.9   61999.4
  526280  5253955.9   62025.7
  526284.1    5253955.9   62064.8
  526288.2    5253955.9   62068.6
  526292.3    5253955.9   62099.2
  526296.4    5253955.9   62172.6
  526300.6    5253955.9   62283.8
  526304.7    5253955.9   62440.8
  526308.8    5253955.9   62458.1
  526312.9    5253955.9   62588.3
  526317  5253955.9   62521.1
  526321.1    5253955.9   62390.8
  526325.2    5253955.9   62310.4
  526329.3    5253955.9   62271
  526333.4    5253955.9   62214.3
  526337.6    5253955.9   62118.8
  526341.7    5253955.9   62024.5
  526345.8    5253955.9   61989.4
  526349.9    5253955.9   61943.5
  526354  5253955.9   61835.8
  
  526506.1    5253955.9   61915.8
  526510.2    5253955.9   62043
  526514.3    5253955.9   62039.2
  526518.4    5253955.9   62021.1
  526522.6    5253955.9   62014
  526526.7    5253955.9   61930.3
  526530.8    5253955.9   61880.7
  526534.9    5253955.9   61758.4
  526539  5253955.9   61733.5
  526543.1    5253955.9   61787.5
  526547.2    5253955.9   61862.6
  526551.3    5253955.9   61934.6
  526555.4    5253955.9   61990.5
  526559.6    5253955.9   62059.5
  526563.7    5253955.9   62092
  526567.8    5253955.9   62104.3
  526571.9    5253955.9   62146.3
  526576  5253955.9   62242.9
  526580.1    5253955.9   62420.5
  526584.2    5253955.9   62204.1
  526588.3    5253955.9   62178.4
  526592.4    5253955.9   62159
  526596.6    5253955.9   62147.1
  526600.7    5253955.9   62159.6
  526604.8    5253955.9   62144.3
  526608.9    5253955.9   62131.1
  526613  5253955.9   62121.7
  526617.1    5253955.9   62117.9
  526621.2    5253955.9   62084.7
  526625.3    5253955.9   62139.2
  526629.4    5253955.9   62136.5
  526633.6    5253955.9   62142
  526637.7    5253955.9   62144.3
  526641.8    5253955.9   62250.2
  526645.9    5253955.9   62274.5
  526650  5253955.9   62119
  526243  5253960 62104
  526247.1    5253960 62041.8
  526251.2    5253960 61978.7
  526255.3    5253960 61993.8
  526259.4    5253960 61998.6
  526263.6    5253960 61981
  526267.7    5253960 61982
  526271.8    5253960 61995.3
  526275.9    5253960 62010.1
  526280  5253960 62030.7
  526284.1    5253960 62061.3
  526288.2    5253960 62089.9
  526292.3    5253960 62115.6
  526296.4    5253960 62205.4
  526300.6    5253960 62319.9
  526304.7    5253960 62392.1
  526308.8    5253960 62434.8
  526312.9    5253960 62466.7
  526317  5253960 62479.9
  526321.1    5253960 62358.1
  526325.2    5253960 62281.7
  526329.3    5253960 62214.8
  526333.4    5253960 62131.9
  526382.8    5253960 61613.3
  526386.9    5253960 61591.6
  526391  5253960 61406.2
  526395.1    5253960 61179.4
  526399.2    5253960 61291.8
  526403.3    5253960 61307.2
  526407.4    5253960 61304.3
  526411.6    5253960 61320.5
  526415.7    5253960 61376.8
  526419.8    5253960 61160.5
  526423.9    5253960 61045.8
  526428  5253960 61138.2
  526432.1    5253960 61113.1
  526436.2    5253960 60926.6
  526440.3    5253960 60793.8
  526444.4    5253960 60775.6
  526448.6    5253960 60776.9
  526452.7    5253960 60979.6
  526456.8    5253960 61309.1
  526460.9    5253960 61772.9
  526465  5253960 61665.1
  526469.1    5253960 61554.1
  526473.2    5253960 61569.5
  526477.3    5253960 61725.2
  526481.4    5253960 61846
  526485.6    5253960 61948.4
  526489.7    5253960 61944.3
  526493.8    5253960 61848
  526497.9    5253960 61677.3
  526502  5253960 61516.1
  526506.1    5253960 61634.4
  526510.2    5253960 61884.9
  526514.3    5253960 61975.8
  526518.4    5253960 61909.8
  526522.6    5253960 61905.6
  526526.7    5253960 61835
  526530.8    5253960 61692.3
  526534.9    5253960 61408.4
  526539  5253960 61533.9
  526543.1    5253960 61670.4
  526547.2    5253960 61785.9
  526551.3    5253960 61878.6
  526555.4    5253960 61963.3
  526559.6    5253960 62048.6
  526563.7    5253960 62070.7
  526567.8    5253960 62099.5
  526571.9    5253960 62140.9
  526576  5253960 62242.6
  526580.1    5253960 62255
  526584.2    5253960 62171.5
  526588.3    5253960 62180.7
  526592.4    5253960 62164.1
  526596.6    5253960 62158.9
  526600.7    5253960 62147.7
  526604.8    5253960 62146.6
  526608.9    5253960 62129
  526613  5253960 62122.5
  526617.1    5253960 62114.6
  526621.2    5253960 62080.8
  526625.3    5253960 62140.4
  526629.4    5253960 62142.5
  526633.6    5253960 62149.3
  526637.7    5253960 62152
  526641.8    5253960 62263.4
  526645.9    5253960 62291.9
  526650  5253960 62286.3
  526243  5253964.1   62092
  526247.1    5253964.1   62041.8
  526251.2    5253964.1   61978.3
  526255.3    5253964.1   62000.1
  526259.4    5253964.1   62012.2
  526263.6    5253964.1   62027.1
  526267.7    5253964.1   62001.6
  526271.8    5253964.1   62003.2
  526275.9    5253964.1   61988.3
  526280  5253964.1   62028.8
  526284.1    5253964.1   62056.9
  526288.2    5253964.1   62075.6
  526292.3    5253964.1   62149.4
  526296.4    5253964.1   62248
  526300.6    5253964.1   62365.5
  526555.4    5253964.1   61980.9
  526559.6    5253964.1   62035.4
  526563.7    5253964.1   62055.7
  526567.8    5253964.1   62100.7
  526571.9    5253964.1   62146.3
  526576  5253964.1   62199
  526580.1    5253964.1   62195.8
  526584.2    5253964.1   62152.1
  526588.3    5253964.1   62147.5
  526592.4    5253964.1   62192.7
  526596.6    5253964.1   62123.1
  526600.7    5253964.1   62114
  526604.8    5253964.1   62115.9
  526608.9    5253964.1   62108.7
  526613  5253964.1   62106.3
  526617.1    5253964.1   62101.6
  526621.2    5253964.1   62065.8
  526625.3    5253964.1   62131
  526629.4    5253964.1   62133.5
  526633.6    5253964.1   62139.8
  526637.7    5253964.1   62143
  526641.8    5253964.1   62245.9
  526645.9    5253964.1   62265.8
  526650  5253964.1   62302.6
  526243  5253968.3   62086
  526247.1    5253968.3   62035.9
  526251.2    5253968.3   61980
  526255.3    5253968.3   61995.1
  526259.4    5253968.3   62021.7
  526263.6    5253968.3   62012.6
  526267.7    5253968.3   61992.3
  526271.8    5253968.3   62024.4
  526275.9    5253968.3   61968.1
  526280  5253968.3   62030.8
  526284.1    5253968.3   62045.5
  526288.2    5253968.3   62092.9
  526292.3    5253968.3   62189.2
  526296.4    5253968.3   62316.8
  526300.6    5253968.3   62476.9
  526304.7    5253968.3   62513.2
  526308.8    5253968.3   62437.8
  526312.9    5253968.3   62356.8
  526317  5253968.3   62305.8
  526321.1    5253968.3   62248.8
  526325.2    5253968.3   62187.3
  526329.3    5253968.3   62115.2
  526333.4    5253968.3   62031
  526337.6    5253968.3   62028.7
  526341.7    5253968.3   61980.8
  526345.8    5253968.3   61979.9
  526349.9    5253968.3   61825.2
  526354  5253968.3   61721.9
  526358.1    5253968.3   61733.8
  526362.2    5253968.3   61654.4
  526366.3    5253968.3   61493.2
  526370.4    5253968.3   61363.9
  526374.6    5253968.3   61270.6
  526378.7    5253968.3   61302.3
  526382.8    5253968.3   61352.9
  526386.9    5253968.3   61309
  526391  5253968.3   61151.5
  526395.1    5253968.3   60971.2
  526399.2    5253968.3   60867.7
  526403.3    5253968.3   60888.3
  526407.4    5253968.3   60935
  526411.6    5253968.3   60938.5
  526415.7    5253968.3   61003.7
  526419.8    5253968.3   61103.4
  526423.9    5253968.3   60876.9
  526428  5253968.3   60551.8
  526432.1    5253968.3   60572.6
  526436.2    5253968.3   60717
  526440.3    5253968.3   60755.9
  526444.4    5253968.3   60572.4
  526448.6    5253968.3   60121.9
  526563.7    5253968.3   62039.3
  526567.8    5253968.3   62088.7
  526571.9    5253968.3   62134.1
  526576  5253968.3   62154.3
  526580.1    5253968.3   62181.4
  526584.2    5253968.3   62209.6
  526588.3    5253968.3   62200.7
  526592.4    5253968.3   62210.8
  526596.6    5253968.3   62184.9
  526600.7    5253968.3   62175.3
  526604.8    5253968.3   62120.9
  526608.9    5253968.3   62105.4
  526613  5253968.3   62100.4
  526617.1    5253968.3   62089.4
  526621.2    5253968.3   62048.4
  526625.3    5253968.3   62109.9
  526629.4    5253968.3   62118.6
  526633.6    5253968.3   62114.2
  526637.7    5253968.3   62122.6
  526641.8    5253968.3   62244.9
  526645.9    5253968.3   62267.5
  526650  5253968.3   62310.7
  526243  5253972.4   62069.2
  526247.1    5253972.4   62038.8
  526251.2    5253972.4   62000.6
  526255.3    5253972.4   62021.2
  526259.4    5253972.4   62007
  526263.6    5253972.4   62003.1
  526267.7    5253972.4   62021.6
  526271.8    5253972.4   62052.7
  526275.9    5253972.4   62073.4
  526280  5253972.4   62056.2
  526284.1    5253972.4   62089.7
  526288.2    5253972.4   62148.2
  526292.3    5253972.4   62244.1
  526296.4    5253972.4   62372
  526300.6    5253972.4   62451.7
  526304.7    5253972.4   62476
  526308.8    5253972.4   62392.1
  526312.9    5253972.4   62354.4
  526317  5253972.4   62276.2
  526321.1    5253972.4   62209.1
  526325.2    5253972.4   62164.2
  526329.3    5253972.4   62089.1
  526333.4    5253972.4   62038.1
  526337.6    5253972.4   61983.1
  526341.7    5253972.4   61910.2
  526345.8    5253972.4   61794.9
  526349.9    5253972.4   61654
  526354  5253972.4   61547
  526358.1    5253972.4   61532.1
  526362.2    5253972.4   61464.3
  526366.3    5253972.4   61343.5
  526370.4    5253972.4   61173
  526374.6    5253972.4   61061.3
  526378.7    5253972.4   61041.7
  526382.8    5253972.4   61234.2
  526386.9    5253972.4   61196.5
  526391  5253972.4   61047.1
  526395.1    5253972.4   60856.4
  526399.2    5253972.4   60764.9
  526403.3    5253972.4   60778.6
  526407.4    5253972.4   60836.6
  526411.6    5253972.4   60887.4
  526415.7    5253972.4   61012
  526419.8    5253972.4   61134.9
  526423.9    5253972.4   60972.7
  526428  5253972.4   60599.3
  526432.1    5253972.4   60154.9
  526436.2    5253972.4   60802.8
  526440.3    5253972.4   60958.2
  526444.4    5253972.4   60530.1
  526448.6    5253972.4   60229.9
  526452.7    5253972.4   60197.6
  526456.8    5253972.4   60425.8
  526460.9    5253972.4   60450.8
  526465  5253972.4   59787.6
  526469.1    5253972.4   59404.4
  526473.2    5253972.4   60447.7
  526477.3    5253972.4   61011.9
  526481.4    5253972.4   61304
  526485.6    5253972.4   61404
  526489.7    5253972.4   61431.8
  526493.8    5253972.4   61455.5
  526497.9    5253972.4   61489.8
  526502  5253972.4   61445.9
  526506.1    5253972.4   61581.3
  526510.2    5253972.4   61723.1
  526514.3    5253972.4   61744.5
  526518.4    5253972.4   61759.3
  526522.6    5253972.4   61651.6
  526526.7    5253972.4   61357.4
  526530.8    5253972.4   61088.1
  526534.9    5253972.4   61505.6
  526539  5253972.4   61793.5
  526543.1    5253972.4   61846.8
  526547.2    5253972.4   61890.7
  526551.3    5253972.4   61929
  526555.4    5253972.4   61953.5
  526559.6    5253972.4   62004
  526563.7    5253972.4   62017.1
  526567.8    5253972.4   62069.5
  526571.9    5253972.4   62119.6
  526576  5253972.4   62142.3
  526580.1    5253972.4   62190.1
  526584.2    5253972.4   62239.9
  526588.3    5253972.4   62268.3
  526592.4    5253972.4   62257.5
  526596.6    5253972.4   62212.8
  526600.7    5253972.4   62193.3
  526604.8    5253972.4   62137
  526608.9    5253972.4   62084.3
  526613  5253972.4   62075.9
  526617.1    5253972.4   62072.8
  526621.2    5253972.4   62030.6
  526625.3    5253972.4   62100.9
  526629.4    5253972.4   62107.4
  526633.6    5253972.4   62124.6
  526637.7    5253972.4   62140.9
  526641.8    5253972.4   62249.8
  526645.9    5253972.4   62275.2
  526650  5253972.4   62325
  526243  5253976.5   62069.2
  526247.1    5253976.5   62037.5
  526251.2    5253976.5   61984.2
  526255.3    5253976.5   62000.4
  526259.4    5253976.5   62020.3
  526263.6    5253976.5   62019.6
  526267.7    5253976.5   62028.1
  526271.8    5253976.5   62079.9
  526275.9    5253976.5   62095.9
  526280  5253976.5   62084.5
  526284.1    5253976.5   62129.4
  526288.2    5253976.5   62203.6
  526292.3    5253976.5   62304.3
  526296.4    5253976.5   62380.6
  526300.6    5253976.5   62398
  526304.7    5253976.5   62358.6
  526308.8    5253976.5   62323.8
  526312.9    5253976.5   62283
  526317  5253976.5   62240.6
  526321.1    5253976.5   62175.5
  526325.2    5253976.5   62113.9
  526329.3    5253976.5   62021.2
  526333.4    5253976.5   61958.1
  526337.6    5253976.5   61902.3
  526341.7    5253976.5   61846.7
  526345.8    5253976.5   61647.2
  526349.9    5253976.5   61442.7
  526354  5253976.5   61346.2
  526358.1    5253976.5   61387.1
  526362.2    5253976.5   61324.2
  526366.3    5253976.5   61168.7
  526370.4    5253976.5   61043.5
  526374.6    5253976.5   60854.9
  526378.7    5253976.5   60797.1
  526382.8    5253976.5   60889.2
  526386.9    5253976.5   60915.6
  526391  5253976.5   60822.2
  526395.1    5253976.5   60760.4
  526399.2    5253976.5   60700.1
  526403.3    5253976.5   60540.3
  526407.4    5253976.5   60525.5
  526411.6    5253976.5   60693.8
  526415.7    5253976.5   60905.6
  526419.8    5253976.5   61065.2
  526423.9    5253976.5   60992.9
  526428  5253976.5   60873.2
  526432.1    5253976.5   60135.2
  526436.2    5253976.5   60421.8
  526440.3    5253976.5   60699.9
  526444.4    5253976.5   60422.8
  526448.6    5253976.5   60075.5
  526452.7    5253976.5   59948.4
  526456.8    5253976.5   60170.3
  526460.9    5253976.5   60534
  526465  5253976.5   59849.7
  526469.1    5253976.5   59221.9
  526473.2    5253976.5   59961.2
  526477.3    5253976.5   60589
  526481.4    5253976.5   60958.8
  526485.6    5253976.5   61166
  526489.7    5253976.5   61296.1
  526493.8    5253976.5   61335.3
  526497.9    5253976.5   61448
  526502  5253976.5   61423.1
  526506.1    5253976.5   61574.7
  526510.2    5253976.5   61769.1
  526514.3    5253976.5   61774.9
  526518.4    5253976.5   61847.8
  526522.6    5253976.5   61888.6
  526526.7    5253976.5   61915.7
  526530.8    5253976.5   61965.2
  526534.9    5253976.5   61939
  526539  5253976.5   61954.5
  526543.1    5253976.5   61935.2
  526547.2    5253976.5   61942.9
  526551.3    5253976.5   61951.1
  526555.4    5253976.5   61998.7
  526559.6    5253976.5   61981.4
  526563.7    5253976.5   61991.2
  526567.8    5253976.5   62052.1
  526571.9    5253976.5   62141.2
  526576  5253976.5   62167.5
  526580.1    5253976.5   62175.5
  526584.2    5253976.5   62277.2
  526588.3    5253976.5   62363.1
  526592.4    5253976.5   62262.3
  526596.6    5253976.5   62178.3
  526600.7    5253976.5   62151.2
  526604.8    5253976.5   62143.3
  526608.9    5253976.5   62092.3
  526613  5253976.5   62073.4
  526617.1    5253976.5   62072.3
  526621.2    5253976.5   62030.2
  526625.3    5253976.5   62096.5
  526629.4    5253976.5   62110.7
  526633.6    5253976.5   62115.6
  526637.7    5253976.5   62139
  526641.8    5253976.5   62251.8
  526645.9    5253976.5   62277.1
  526650  5253976.5   62337.3
  526243  5253980.6   62066.3
  526247.1    5253980.6   62048
  526251.2    5253980.6   62002.1
  526255.3    5253980.6   62005.9
  526259.4    5253980.6   62016.9
  526263.6    5253980.6   62024
  526267.7    5253980.6   62054.9
  526271.8    5253980.6   62109.2
  526275.9    5253980.6   62090.7
  526280  5253980.6   62121.7
  526284.1    5253980.6   62169.8
  526288.2    5253980.6   62245.1
  526292.3    5253980.6   62311.2
  526296.4    5253980.6   62336.4
  526300.6    5253980.6   62305.7
  526304.7    5253980.6   62294.3
  526308.8    5253980.6   62252.1
  526312.9    5253980.6   62203
  526317  5253980.6   62172.3
  526321.1    5253980.6   62097.8
  526325.2    5253980.6   62031.2
  526329.3    5253980.6   61944.4
  526333.4    5253980.6   61889.2
  526337.6    5253980.6   61820.7
  526341.7    5253980.6   61742.6
  526345.8    5253980.6   61514
  526349.9    5253980.6   61344.2
  526354  5253980.6   61245.2
  526358.1    5253980.6   61238.2
  526362.2    5253980.6   61181.5
  526366.3    5253980.6   61034
  526370.4    5253980.6   60946.3
  526374.6    5253980.6   60761.3
  526378.7    5253980.6   60579.3
  526382.8    5253980.6   60575.5
  526386.9    5253980.6   60797.7
  526391  5253980.6   60773.6
  526395.1    5253980.6   60771.5
  526399.2    5253980.6   60727.6
  526403.3    5253980.6   60545.5
  526407.4    5253980.6   60405.8
  526411.6    5253980.6   60482.8
  526415.7    5253980.6   60903.6
  526419.8    5253980.6   61087.6
  526423.9    5253980.6   61206.6
  526428  5253980.6   61175.3
  526432.1    5253980.6   60749.5
  526436.2    5253980.6   60558.7
  526440.3    5253980.6   60418
  526444.4    5253980.6   60293.5
  526448.6    5253980.6   60012
  526452.7    5253980.6   59445.5
  526456.8    5253980.6   59617.3
  526460.9    5253980.6   60258.1
  526465  5253980.6   60222.1
  526469.1    5253980.6   59939.5
  526473.2    5253980.6   60081.4
  526477.3    5253980.6   60348.9
  526481.4    5253980.6   60695.2
  526485.6    5253980.6   60930.1
  526489.7    5253980.6   61133.6
  526493.8    5253980.6   61264.2
  526497.9    5253980.6   61349.5
  526502  5253980.6   61355.8
  526506.1    5253980.6   61398.3
  526510.2    5253980.6   61698.9
  526514.3    5253980.6   61786.7
  526518.4    5253980.6   61866.2
  526522.6    5253980.6   62075.3
  526526.7    5253980.6   62405.3
  526530.8    5253980.6   62759.8
  526534.9    5253980.6   62307.7
  526539  5253980.6   62091.4
  526543.1    5253980.6   61996.8
  526547.2    5253980.6   61953.2
  526551.3    5253980.6   61935.6
  526555.4    5253980.6   61932.6
  526559.6    5253980.6   61922.5
  526563.7    5253980.6   61940.6
  526567.8    5253980.6   61991.2
  526571.9    5253980.6   62040.7
  526576  5253980.6   62075.9
  526580.1    5253980.6   62104.3
  526584.2    5253980.6   62151.5
  526588.3    5253980.6   62193.7
  526592.4    5253980.6   62166.6
  526596.6    5253980.6   62121.4
  526600.7    5253980.6   62098.5
  526604.8    5253980.6   62100
  526608.9    5253980.6   62070.9
  526613  5253980.6   62061.9
  526617.1    5253980.6   62064.2
  526621.2    5253980.6   62018.3
  526625.3    5253980.6   62088.8
  526629.4    5253980.6   62102.2
  526633.6    5253980.6   62107.7
  526637.7    5253980.6   62133.7
  526641.8    5253980.6   62251.3
  526645.9    5253980.6   62280.6
  526650  5253980.6   62348
  526243  5253984.7   62070.5
  526247.1    5253984.7   62032.9
  526251.2    5253984.7   61995.8
  526255.3    5253984.7   62013.9
  526259.4    5253984.7   62021.1
  526263.6    5253984.7   62031.5
  526267.7    5253984.7   62062.8
  526271.8    5253984.7   62111.6
  526275.9    5253984.7   62114.9
  526280  5253984.7   62139
  526284.1    5253984.7   62200.9
  526288.2    5253984.7   62248.8
  526292.3    5253984.7   62278.6
  526296.4    5253984.7   62268.5
  526300.6    5253984.7   62259.9
  526304.7    5253984.7   62234.8
  526308.8    5253984.7   62189.8
  526312.9    5253984.7   62159.2
  526317  5253984.7   62085
  526321.1    5253984.7   62005
  526325.2    5253984.7   61934.3
  526329.3    5253984.7   61855.4
  526333.4    5253984.7   61811.4
  526337.6    5253984.7   61785.8
  526341.7    5253984.7   61567.1
  526345.8    5253984.7   61412.7
  526349.9    5253984.7   61300.2
  526354  5253984.7   61168
  526358.1    5253984.7   61129.6
  526362.2    5253984.7   61029.5
  526366.3    5253984.7   60792.3
  526370.4    5253984.7   60739
  526374.6    5253984.7   60601.2
  526378.7    5253984.7   60352.3
  526382.8    5253984.7   60250.4
  526386.9    5253984.7   60371.7
  526391  5253984.7   60576.7
  526395.1    5253984.7   60709.4
  526399.2    5253984.7   60647.8
  526403.3    5253984.7   60407.7
  526407.4    5253984.7   60270.3
  526411.6    5253984.7   60235.8
  526415.7    5253984.7   60576.9
  526419.8    5253984.7   60782.5
  526423.9    5253984.7   61177.2
  526428  5253984.7   61308.1
  526432.1    5253984.7   61268.4
  526436.2    5253984.7   60831.1
  526440.3    5253984.7   60244.9
  526444.4    5253984.7   60060.9
  526448.6    5253984.7   60139.4
  526452.7    5253984.7   59810.3
  526456.8    5253984.7   59954
  526460.9    5253984.7   60277.9
  526465  5253984.7   60327.2
  526469.1    5253984.7   60454.4
  526473.2    5253984.7   60387.6
  526477.3    5253984.7   60202.1
  526481.4    5253984.7   60292.2
  526485.6    5253984.7   60657.1
  526489.7    5253984.7   60909
  526493.8    5253984.7   61070.8
  526497.9    5253984.7   61128.9
  526502  5253984.7   61233.6
  526506.1    5253984.7   61286.2
  526510.2    5253984.7   61543.5
  526514.3    5253984.7   61691.4
  526518.4    5253984.7   61822.6
  526522.6    5253984.7   62016.1
  526526.7    5253984.7   62274.3
  526530.8    5253984.7   62299.4
  526534.9    5253984.7   62263.7
  526539  5253984.7   62161.4
  526543.1    5253984.7   62070.3
  526547.2    5253984.7   61992.3
  526551.3    5253984.7   61919.4
  526555.4    5253984.7   61842.4
  526559.6    5253984.7   61810.8
  526563.7    5253984.7   61862.3
  526567.8    5253984.7   61926.4
  526571.9    5253984.7   61919
  526576  5253984.7   61948.4
  526580.1    5253984.7   61989.3
  526584.2    5253984.7   62017
  526588.3    5253984.7   62065.8
  526592.4    5253984.7   62058.4
  526596.6    5253984.7   62053.2
  526600.7    5253984.7   62041.8
  526604.8    5253984.7   62066.9
  526608.9    5253984.7   62072.8
  526613  5253984.7   62072.4
  526617.1    5253984.7   62055.3
  </code></pre>
  
  <p>Sorry about the miss-aligned entries, this comes from copying out of MS Excel...</p>
  
  <p>The data is arranged as a series of lines which when combined constitute a list of co-ordinates from a grid over an area bounded by the upper and lower most points' 'x' and 'y' values.</p>
  
  <p>The problem which caused my script to hang was that the sub-sampled data set, which I was trying to grid in order to compare a countour image of it with the master dataset, had mis-aligned line start and end points.  This was true for all sub-sampled datasets which were created using a sub interval of an odd number.</p>
  
  <p>I fixed the problem by using an additional check in a 'for' loop which sub-sampled the dataset.</p>
  
  <p>Here is the fixed 'sub-sample' code.</p>
  
  <pre><code> - Note: The plotting code works seamlessly.
  
      def sub_sample():
          print ""
          print " - This program will sub-sample a dataset for every &lt;n&gt; datapoint."
          print " - &lt;n&gt; should realistically should be between 1 and 10."
          print " - If &lt;n&gt; &gt; 10, interpretation confidence is reduced significantly."
          print ""
          n = raw_input(" - What value should &lt;n&gt; take?: ")
  
          if int(n) &gt; 0 and int(n) &lt; 2001:
              print ""
              print " - You have chosen to subsample the data every "+str(n)+" datapoints."
  
              perc = (float(1)/float(n)*int(100))
              print " - This corresponds to "+str(perc)+" percent of the data."
  
              indataarray = numpy.loadtxt("out.csv", skiprows=1, delimiter=',')
  
              out_name = "every_"+str(n)+".csv"     
  
              t = indataarray.shape
              totalrows = t[0]
              totalcolumns = t[1]
              holding_array = numpy.zeros( [totalrows, totalcolumns] )
  
              for i in range(totalrows):
  
                  if ((i % 100) % int(n) == 0):
                      for j in range(totalcolumns):
                          holding_array[i,j] = indataarray[i,j] 
  
              no_zeros = (holding_array == 0).sum(1)
              new_holding = holding_array[no_zeros == 0, :]
              numpy.savetxt(out_name, new_holding, delimiter=',', fmt='%f')
  
              hdr_c1 = 'Easting,'
              hdr_c2 = 'Northing,'
              hdr_c3 = 'TMI_nT'
  
              f = open(out_name)
              text = f.read()
              f.close()
  
              f = open(out_name, 'w')
              f.write(hdr_c1+hdr_c2+hdr_c3+'\n')
              f.write(text)
              f.close
              print " - The file "+out_name+" has been created."
  
          else:
              print ""
              print " - You have entered an unrealistic value for &lt;n&gt;."
              print " - Please try again."
              sub_sample()
  </code></pre>