title: how to make a Pixel picture in R
body: <p>I have a data.frame as this:</p>
  
  <pre><code>&gt; head(shht)
    tt2 imf           f        a
  1   1  c1 0.025735102 461.1430
  2   2  c1 0.025735102 336.5967
  3   3  c1 0.012977971 334.0539
  4   4  c1 0.013013110 303.7454
  5   5  c1 0.009130993 301.7031
  6   6  c1 0.009153142 287.5305
  </code></pre>
  
  <p>the data is <a href="https://drive.google.com/open?id=0B3bNSNFik5wGNGY4VEQ0TFltM3M" rel="nofollow noreferrer">here</a></p>
  
  <p>There are a total of four columns. I want to draw a pixmap. The first column is the horizontal axis, the third column is the vertical axis, and the fourth column is the grayscale value.</p>
  
  <p>I tried the following:</p>
  
  <pre><code>&gt; simage=as.image(shht$a,x=cbind(shht$tt2,shht$f))
  &gt; image.plot.ts(simage,tt=tt2)
  Error in plot.new() : figure margins too large
  </code></pre>
  
  <p>the image.plot.ts() is a function from EMD. and the as.image() comes from fields.</p>