83

The plotting code below gives Error: Discrete value supplied to continuous scale

What's wrong with this code? It works fine until I try to change the scale so the error is there... I tried to figure out solutions from similar problem but couldn't.

meltDF <- data.frame( MW = c( 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4, 3.9, 6.4, 7.4, 8.1, 9, 9.4 ), variable = factor( c( "10", "10", "10", "10", "10", "10", "33.95", "33.95", "33.95", "33.95", "33.95", "33.95", "58.66", "58.66", "58.66", "58.66", "58.66", "58.66", "84.42", "84.42", "84.42", "84.42", "84.42", "84.42", "110.21", "110.21", "110.21", "110.21", "110.21", "110.21", "134.16", "134.16", "134.16", "134.16", "134.16", "134.16", "164.69", "164.69", "164.69", "164.69", "164.69", "164.69", "199.1", "199.1", "199.1", "199.1", "199.1", "199.1", "234.35", "234.35", "234.35", "234.35", "234.35", "234.35", "257.19", "257.19", "257.19", "257.19", "257.19", "257.19", "361.84", "361.84", "361.84", "361.84", "361.84", "361.84", "432.74", "432.74", "432.74", "432.74", "432.74", "432.74", "506.34", "506.34", "506.34", "506.34", "506.34", "506.34", "581.46", "581.46", "581.46", "581.46", "581.46", "581.46", "651.71", "651.71", "651.71", "651.71", "651.71", "651.71", "732.59", "732.59", "732.59", "732.59", "732.59", "732.59", "817.56", "817.56", "817.56", "817.56", "817.56", "817.56", "896.24", "896.24", "896.24", "896.24", "896.24", "896.24", "971.77", "971.77", "971.77", "971.77", "971.77", "971.77", "1038.91", "1038.91", "1038.91", "1038.91", "1038.91", "1038.91" ), levels = c( "10", "33.95", "58.66", "84.42", "110.21", "134.16", "164.69", "199.1", "234.35", "257.19", "361.84", "432.74", "506.34", "581.46", "651.71", "732.59", "817.56", "896.24", "971.77", "1038.91" ) ), value = c( 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0 ) )

The plotting code:

## Plotting ggplot(meltDF[meltDF$value == 1,]) + geom_point(aes(x = MW, y = variable)) + scale_x_continuous(limits=c(0, 1200), breaks=c(0, 400, 800, 1200)) + scale_y_continuous(limits=c(0, 1200), breaks=c(0, 400, 800, 1200))

Here's how the plot looked before adding scale:

Plot

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4
  • 12
    Your y values (variable) are factor, so you can't use scale_y_continuous. Commented Mar 26, 2015 at 12:21
  • 1
    Any quick solution how to change it into numeric or the one which is required ? Thanks! Commented Mar 26, 2015 at 12:23
  • 1
    stackoverflow.com/questions/3418128/… Commented Mar 26, 2015 at 12:45
  • 1
    Tried couple of solution but it doesn't work or I do it incorrectly. Commented Mar 26, 2015 at 13:29

3 Answers 3

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60

As mentioned in the comments, there cannot be a continuous scale on variable of the factor type. You could change the factor to numeric as follows, just after you define the meltDF variable.

meltDF$variable=as.numeric(levels(meltDF$variable))[meltDF$variable]

Then, execute the ggplot command

 ggplot(meltDF[meltDF$value == 1,]) + geom_point(aes(x = MW, y = variable)) + scale_x_continuous(limits=c(0, 1200), breaks=c(0, 400, 800, 1200)) + scale_y_continuous(limits=c(0, 1200), breaks=c(0, 400, 800, 1200))

And you will have your chart.

Hope this helps

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Comments

35

if x is numeric, then add scale_x_continuous(); if x is character/factor, then add scale_x_discrete(). This might solve your problem.

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8

In my case, you need to convert the column(you think this column is numeric, but actually not) to numeric

geom_segment(data=tmpp, aes(x=start_pos, y=lib.complexity, xend=end_pos, yend=lib.complexity) ) # to geom_segment(data=tmpp, aes(x=as.numeric(start_pos), y=as.numeric(lib.complexity), xend=as.numeric(end_pos), yend=as.numeric(lib.complexity)) )
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