title: Modify markers/lines for two legends separately in R
body: <p>My plot below consists of contour lines from a density estimate and several points, which are colored by the number of experiments. The legend for the contour lines is indicated by the alpha values, which is based on the level of the contour. The legend for the points are based on color and shape. When I try to modify the size of the points in the second legend, it also modifies the points for the first (level) legend. I'd like to</p>
  <ol>
  <li>Remove the markers in the level legend and keep only the lines.</li>
  <li>Remove the lines in the points legend (Num. Experiments) and keep only the markers.</li>
  </ol>
  <p>I tried to use the grid package to modify the elements, but I'm lost as two what element in the grobs I should be extracting.</p>
  <pre><code> plt &lt;- ggplot() +
    facet_grid(Ylab~subtype)+
    geom_point(data=subset(All_subtypes_CD27_57_45,disc_comb_label&gt;0),
               aes(x=CD45RO,y=Y,
                   color=factor(disc_comb_label),
                   shape=factor(disc_comb_label)),
               size=0.3,stroke=0.4,alpha=0.7,show.legend = TRUE) +
    stat_density_2d(data=subset(All_subtypes_CD27_57_45,disc_comb_label==0),
                    geom = &quot;density2d&quot;, contour = TRUE,
                    aes(x=CD45RO,y=Y,alpha=..level..),
                    color = &quot;black&quot;,
                    bins = 20,
                    show.legend=TRUE) +
    labs(col=&quot;Num. Experiments&quot;,shape=&quot;Num. Experiments&quot;) +
    theme_light() +
    theme(axis.title.y = element_blank())
  
  plt
  grid::grid.ls(grid::grid.force())
  
  # Set the size of the point in the legend to 4 mm
  grid::grid.gedit(&quot;key-[-0-9]-1-1&quot;, size = unit(4, &quot;mm&quot;))
  
  # save the modified plot to an object
  plt2 &lt;- grid::grid.grab()
  ggsave(plt2, filename = 'plt2.jpg')
  </code></pre>
  <p><a href="https://i.stack.imgur.com/il9Zw.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/il9Zw.jpg" alt="Example Plot" /></a></p>
  <p><strong>Edit</strong></p>
  <p>Here is a sample (n=100) of my data. Note: the <code>bins</code> parameter in <code>stat_density_2d</code> should be changed to a smaller number.</p>
  <pre><code>structure(list(Y = c(0.284191844029658, 0.558504950709616, 0.315535249343904, 
  0.300977792187569, 0.476751857332456, 0.484240073554636, 0.307618222739758, 
  0.382774310068314, 0.251491191205721, 0.28867075547189, 0.48023653568676, 
  0.687385202552218, 0.348302145404881, 0.284956590469867, 0.449212367426197, 
  0.0541572395716273, 0.43091149290646, 0.475086982205484, 0.245475455526474, 
  0.320922298535602, 0.433582014376387, 0.454556959163362, 0.519150252727787, 
  0.501333864070255, 0.485212214204431, 0.477742661471719, 0.141047727372665, 
  0.455451223886891, 0.445897410519097, 0.405296464170209, 0.383655314069156, 
  0.213964454993715, 0.242076596187618, 0.298039605455974, 0.157815389237226, 
  0.510987159437738, 0.228542986920969, 0.348112572853986, 0.149900990492508, 
  0.390457313763976, 0.530735405696848, 0.213071719254767, 0.241746672739817, 
  0.109465638906155, 0.2119121647415, 0.252433268896037, 0.271972455301221, 
  0.434829111969484, 0.139716827881697, 0.342203160239369, 0.604210909752249, 
  0.161481369781311, 0.514151082252664, 0.826880955040602, 0.278455388719208, 
  0.457955173141471, 0.223481509755878, 0.281433841010683, 0.265601344949778, 
  0.272361939825042, 0.36767244848865, 0.200105787104064, 0.297752168002793, 
  0.188282485134585, 0.33643615610689, 0.395965507439215, 0.0890174556246681, 
  0.417612455377232, 0.19887950366616, 0.465049525577064, 0.43789996897205, 
  0.233188419733737, 0.472491498664791, 0.490773751335154, 0.283266705976633, 
  0.401634634651268, 0.45359606927769, 0.20839301810666, 0.441058569024316, 
  0.276163969969656, 0.431188894873133, 0.237522516690592, 0.233077805700025, 
  0.297329147941213, 0.42710702221155, 0.3907243000129, 0.465552001533375, 
  0.437707004564491, 0.384245170961772, 0.142554943891278, 0.435330262145555, 
  0.284103620665539, 0.2032116293577, 0.414955141708168, 0.345017391130214, 
  0.248463896517405, 0.339817523912329, 0.459771971558186, 0.468755486667213, 
  0.510785855184823), CD45RO = c(0.525726398529141, 0.304474523564729, 
  0.612153302344189, 0.612445867565633, 0.249006124636231, 0.0630792385460927, 
  0.634621606796433, 0.252505566525164, 0.58427415301859, 0.604953653422854, 
  0.59367781186968, 0.548146880829038, 0.67686535460711, 0.079010054101595, 
  0.634599315045999, 0.13187972282609, 0.621565232085858, 0.596574983786016, 
  0.110399227872914, 0.658258800443354, 0.187991482962981, 0.650987717469758, 
  0.596006502059151, 0.308912127599816, 0.141884410965155, 0.114224151171362, 
  0.190296706882678, 0.0868622977334288, 0.63084574911242, 0.584149459993462, 
  0.565119489277156, 0.262145879230163, 0.275739650088701, 0.628409611625278, 
  0.106602930270878, 0.107132119095279, 0.620913668866589, 0.624362488858585, 
  0.233756876594812, 0.655615553883786, 0.54873101008282, 0.566443932082788, 
  0.561891801854012, 0.621932759341326, 0.552259106473471, 0.56920228491713, 
  0.602947665552384, 0.696337649780824, 0.660389489026038, 0.584038886021908, 
  0.468975660037085, 0.333155729501406, 0.0495060776252205, 0.16990324928303, 
  0.193105192142293, 0.181173895819966, 0.150182889940719, 0.543052295456474, 
  0.283001532733579, 0.303728587073113, 0.183658577822127, 0.592509419580238, 
  0.714762268117432, 0.128905862697456, 0.638109641089135, 0.654036824302771, 
  0.339947661585455, 0.594245937801801, 0.490577748124374, 0.22853081037735, 
  0.185257260802601, 0.533315410258717, 0.626633178546256, 0.199126070652748, 
  0.188082776802629, 0.635724850685052, 0.638027785005966, 0.608592892283015, 
  0.613768324429073, 0.680925083206514, 0.722032485457904, 0.143070125871505, 
  0.633443738551264, 0.308183097921232, 0.619142922059335, 0.335770730782286, 
  0.291214123731697, 0.142393299180996, 0.252553809505749, 0.423003230545203, 
  0.568276957780311, 0.484324230817047, 0.285551015338659, 0.524580106114011, 
  0.680325288283035, 0.348542443973256, 0.581367577522363, 0.321724942946382, 
  0.0778090215803436, 0.231216025188849), disc_comb_label = c(2, 
  1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 3, 0, 1, 
  5, 2, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 2, 0, 0, 
  0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 2, 0, 0, 0, 0, 0, 0, 0, 
  1, 6, 2, 0, 1, 0, 1, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
  0, 2, 2, 0, 0, 0, 0, 1, 3, 4, 0, 0, 2, 0, 2), Ylab = c(&quot;CD27&quot;, 
  &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD27&quot;, 
  &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD27&quot;, 
  &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD27&quot;, 
  &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD57&quot;, 
  &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD27&quot;, 
  &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD57&quot;, 
  &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD57&quot;, 
  &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD27&quot;, 
  &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD27&quot;, 
  &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD27&quot;, 
  &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD57&quot;, 
  &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD57&quot;, &quot;CD27&quot;, &quot;CD27&quot;, 
  &quot;CD27&quot;, &quot;CD27&quot;, &quot;CD27&quot;), subtype = c(&quot;CD4-CD8+&quot;, &quot;CD4+CD8+&quot;, 
  &quot;CD4-CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8+&quot;, &quot;CD4-CD8+&quot;, 
  &quot;CD4+CD8-&quot;, &quot;CD4+CD8+&quot;, &quot;CD4+CD8+&quot;, &quot;CD4+CD8+&quot;, &quot;CD4+CD8+&quot;, &quot;CD4-CD8+&quot;, 
  &quot;CD4+CD8-&quot;, &quot;CD4-CD8+&quot;, &quot;CD4-CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, 
  &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4-CD8+&quot;, &quot;CD4-CD8+&quot;, &quot;CD4+CD8+&quot;, 
  &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4-CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8+&quot;, 
  &quot;CD4+CD8-&quot;, &quot;CD4+CD8+&quot;, &quot;CD4+CD8+&quot;, &quot;CD4+CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8+&quot;, 
  &quot;CD4-CD8+&quot;, &quot;CD4-CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4-CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, 
  &quot;CD4+CD8-&quot;, &quot;CD4-CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4-CD8+&quot;, 
  &quot;CD4-CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4-CD8+&quot;, &quot;CD4-CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8+&quot;, 
  &quot;CD4+CD8-&quot;, &quot;CD4+CD8+&quot;, &quot;CD4+CD8+&quot;, &quot;CD4-CD8+&quot;, &quot;CD4-CD8+&quot;, &quot;CD4+CD8+&quot;, 
  &quot;CD4+CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8+&quot;, 
  &quot;CD4-CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8+&quot;, &quot;CD4-CD8+&quot;, 
  &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8+&quot;, &quot;CD4+CD8-&quot;, 
  &quot;CD4+CD8+&quot;, &quot;CD4-CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8+&quot;, 
  &quot;CD4-CD8+&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4-CD8+&quot;, &quot;CD4-CD8+&quot;, &quot;CD4+CD8-&quot;, 
  &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;, &quot;CD4-CD8+&quot;, &quot;CD4-CD8+&quot;, &quot;CD4+CD8-&quot;, 
  &quot;CD4+CD8-&quot;, &quot;CD4+CD8-&quot;)), row.names = c(NA, -100L), class = &quot;data.frame&quot;)
  </code></pre>