soosus soosus - 3 months ago 216
R Question

R: "Unary operator error" from multiline ggplot2 command

I'm using ggplot2 to do a boxplot comparison of two different species, as indicated by the third column shown below:

> library(reshape2)
> library(ggplot2)
> melt.data = melt(actb.raw.data)

> head(actb.raw.data)
region expression species
1 CG -0.17686667 human
2 CG -0.06506667 human
3 DG 1.04590000 human
4 CA1 1.94093333 human
5 CA2 1.55023333 human
6 CA3 1.75800000 human

> head(melt.data)
region species variable value
1 CG human expression -0.17686667
2 CG human expression -0.06506667
3 DG human expression 1.04590000
4 CA1 human expression 1.94093333
5 CA2 human expression 1.55023333
6 CA3 human expression 1.75800000


However, when I run the following code:

ggplot(combined.data, aes(x = region, y = expression, fill = species)) +
+ geom_boxplot() +
+ scale_fill_manual(values = c("yellow", "orange"))
+ ggtitle("Expression comparisons for ACTB")
+ theme(axis.text.x = element_text(angle=90, face="bold", colour="black"))


I get this error:

> ggplot(actb.raw.data, aes(x = region, y = expression, fill = species)) +
+ + geom_boxplot() +
+ + scale_fill_manual(values = c("yellow", "orange"))
Error in +geom_boxplot() : invalid argument to unary operator
> + ggtitle("ACTB expression in human vs. macaque")
Error in +ggtitle("ACTB expression in human vs. macaque") :
invalid argument to unary operator
> + theme(axis.text.x = element_text(angle=90, face="bold", colour="black"))
Error in inherits(x, "theme") : argument "e2" is missing, with no default


This also happens when I run using the variable melt.data, for whatever that's worth. Can someone help me fix this? I've run this code successfully before with a different dataset that was formatted identically, and I can't figure out what's going wrong here.

Answer

It looks like you might have inserted an extra + at the beginning of each line, which R is interpreting as a unary operator (like - interpreted as negation, rather than subtraction). I think what will work is

ggplot(combined.data, aes(x = region, y = expression, fill = species)) +
    geom_boxplot() +
    scale_fill_manual(values = c("yellow", "orange")) + 
    ggtitle("Expression comparisons for ACTB") + 
    theme(axis.text.x = element_text(angle=90, face="bold", colour="black"))

Perhaps you copy and pasted from the output of an R console? The console uses + at the start of the line when the input is incomplete.

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