R plot legend colors not showing, random plot colors

Question

I am working with a generic plot fxn that does not know how many lines it will plot until it's completed plotting. The data is plotting just fine, though when I try to create the legend, I'm not getting the colors.

Since the number of lines is unknown I am generating colors for the lines at random; BUT, I am storing the color in a array/vector.

From my code: I understand this is not easily reproduced, but it is not easily dumbed down, as I've gotten to the point of dumbed down and not able to find the problem...

# plot blank plot
plot(1, type="n", xlab="time elapsed [sec]", ylab="Memory Used [MB]", ylim=c(ymin,ymax),   
  xlim=c(xmin,xmax))

 # LOOOOP over column 2 (node)
for(i in 1: length(col2))
{
  if(col2[i] == compareNode)
  {
    #print(paste0("count: ", count))

    # x = time value, y = memory used value for node: compareNode
    x[count] = col1[i]
    y[count] = (col87[i] - col85[i])/1024
    count = count + 1
  }
  else
  {
    # Plot 
    colTest <- sample(colors(), 1)
    mycols <- c(mycols,colTest)
    lines(x, y, col=colTest )

    NODES[nodeCount] = col2[i]
    nodeCount = nodeCount + 1
    # Resets
    compareNode = col2[i]
    x = c()
    y = c()
    count = 1

  }
}

# Plot final line
colTest <- sample(colors(),1)
mycols <- c(mycols,colTest)
lines(x, y, col=colTest)
#print(colors)
legend("topleft", title="LDMS: Memory Used", legend = NODES, col=mycols )
garbage <- dev.off()

Trying for a better example here:

loop x times:
  color <- sample(colors(),1)
  mycols <- c(mycosl,color)
  lines(x,y,col=color)
done
lines(x,y,col=color)   # plots last set of data
legend("topright", title="title", legend=NODES, col=mycols)

There are a bunch of things wrong with your code. If you don't know beforehand how long `colors` will be, how do you take care of its initialization? Second, `legend()` is perfectly able to just use a vector of color names, no need to recode it using `shQuote()`. — meuleman, Aug 19 '14 at 18:19
You should actually provide a [reproducible example](http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example) that we can run and test. Each of these random lines of code do not make much sense on their own. — MrFlick, Aug 19 '14 at 18:20
@meuleman colors can be initiated like any other empty set colors = c() or colors <- c(). I will try to post something more reproduceable. I understand it is difficult to reproduce, but it is also hard to give you all the code as well... — BluePanda, Aug 19 '14 at 18:39
Sure, it can, but it's at the very least bad practice to then fill it up with values by indexing non-existing elements. — meuleman, Aug 19 '14 at 18:41
Well it is the fastest way without pre-parsing the data file to determine how many lines there will be. — BluePanda, Aug 19 '14 at 18:53
Define `mycols <- character(0)` before your for loop. Since you only create it inside an if/else block, it won't exist outside of that block. — MrFlick, Aug 19 '14 at 19:10
It is actually defined above the loop, sorry. should have mycols <- c(). — BluePanda, Aug 19 '14 at 19:11

meuleman · Accepted Answer · 2014-08-19T18:42:55.897

0

Staying as close as possible to your code, and assuming we indeed don't know how many lines we're going to plot:

mycols <- c();
while (sample(1:100, 1) != 14) {
  col <- sample(colors(), 1);
  mycols <- c(mycols, col);
  ##lines(..., col=col) # plot line
}
legend("topleft", title="LDMS: Memory Used", legend = NODES, col=mycols, lty=1)

Better yet, don't just resample 1 element from colors(), but randomize the output of colors() once and then just iterate over it. This will make sure you don't inadvertently reuse any colors.

edited Aug 19 '14 at 18:42

answered Aug 19 '14 at 18:26

meuleman

378
1
7

I like the way you are adding each color to the list much better, but I am still getting a blank legend. :( I will update the OP with more details. – BluePanda Aug 19 '14 at 18:40
add `lty=1` or whatever line type you're using. I've updated my answer. – meuleman Aug 19 '14 at 18:42
I get the warning: Warning in segments(x1, y1, x2, y2, ...) : supplied color is neither numeric nor character; still no color – BluePanda Aug 19 '14 at 18:52
Me neither. Please add a minimal (and working) example to your question. – meuleman Aug 19 '14 at 19:01
I tried to add a bit -- but it is difficult to add anything that can easily be run without my data. Dumbed down I wasn't able to find the problem... – BluePanda Aug 19 '14 at 19:08
Don't forget to add `lty=1` to the `legend()` call. And your new code contains a number of mistakes, most notable a confusion between `col` and `colTest`. Without a better reproducible example there's not much else we can do. – meuleman Aug 19 '14 at 19:12
lty=1 gives me warnings...Warning in segments(x1, y1, x2, y2, ...) : supplied color is neither numeric nor character – BluePanda Aug 19 '14 at 19:13
Right, because you never fill it with anything. Again, check your code for places with `colTest` and `col`. – meuleman Aug 19 '14 at 19:14
I don't mean for it to be confusing, I'm trying to give you as much as I can. I don't know how to give you a reproducible version. I only have what I have – BluePanda Aug 19 '14 at 19:14
I didn't even notice I'd typed col. My apologizes. @meuleman thanks for being patient – BluePanda Aug 19 '14 at 19:19

R plot legend colors not showing, random plot colors

1 Answers1