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I found and example for the %+% operator in ggplot2 to use a different data frame for the same plot. Examples are available here.

When I try this, I get an error message:

df <- data.frame(x=rnorm(1000), y=rnorm(1000))
p <- ggplot(df, aes(x,y)) + geom_point()
p
p %+% df[1:100,]

Error in p %+% df[1:100, ] : x must be either a vector or a matrix

Did I misunderstood the example on the website?

sessionInfo()

sessionInfo()
R version 3.2.0 (2015-04-16)
Platform: x86_64-apple-darwin13.4.0 (64-bit)
Running under: OS X 10.9.5 (Mavericks)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
 [1] cfpscripts_0.4.0  seqinr_3.1-3      ade4_1.7-2        gridExtra_0.9.1   psych_1.5.4       reshape2_1.4.1    plyr_1.8.3        knitr_1.10.5      rMQanalysis_0.2.0 ggplot2_1.0.1     testthat_0.10.0  
[12] devtools_1.8.0   

loaded via a namespace (and not attached):
 [1] Rcpp_0.12.0           git2r_0.10.1          tools_3.2.0           digest_0.6.8          memoise_0.2.1         gtable_0.1.2          lattice_0.20-31       curl_0.8              parallel_3.2.0       
[10] proto_0.3-10          stringr_1.0.0         imbproteomicsr_0.1.7  xml2_0.1.1            rversions_1.0.1       data.table_1.9.4      sp_1.1-1              magrittr_1.5          scales_0.2.5         
[19] cfppdfs_0.3.4         MASS_7.3-40           mnormt_1.5-3          splitstackshape_1.4.2 logspline_2.1.8       colorspace_1.2-6      labeling_0.3          stringi_0.5-5         munsell_0.4.2        
[28] chron_2.3-45          crayon_1.3.0          zoo_1.7-12
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  • 2
    Works for me on ggplot2_1.0.1. Try updating your ggplot2 package. Also you can see if ?"%+%" finds a ggplot2 function Commented Sep 1, 2015 at 14:06
  • 1
    Just figured out that the psych package overwrites the %+% function. Is there a way to call the ggplot2 version explizit? ggplot2::%+% did not work. Commented Sep 1, 2015 at 14:13
  • 4
    load psych before you load ggplot2? or put single-back-quotes around %+% in `ggplot2:``%+%``` Commented Sep 1, 2015 at 14:14
  • Thanks, that solved my question. Commented Sep 1, 2015 at 14:37
  • @BenBolker I wanted to try the ggplot2: notation since it seems to be more stable in case of errors but I can not get it to work. R always complains about unexpected symbol in "p ggplot2". p is my graph and I try ggplot2::'%+%' but the ' are single back ticks which would now highlight my command. I tried also with only one colon, double back ticks and a lot of different combinations but always the same error. Commented Sep 7, 2015 at 12:33

1 Answer 1

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The basic problem is loading the psych package after ggplot2, which gives you a message:

Attaching package: ‘psych’ The following objects are masked from ‘package:ggplot2’: %+%, alpha

Since R's parser allows a limited set of characters to delimit an operator, the ::+back-tick trick p ggplot2::`%+%` newdata won't work. Other than making sure to load psych before ggplot2, you could do 

`%+%` <- ggplot2::`%+%`

to create yet another copy of the operator in your global workspace, but it's probably best just to be careful about loading psych and ggplot2.

You could add a test 

if(find("%+%")[1]=="package:psych") stop("oops")

to your code to make sure this doesn't happen by accident ...

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1 Comment

Actually id did the trick with reassigning the %+% to %myadd% within my function, just to make sure... I work a lot with the psych package and it is often loaded in the background and I didn't wanted to bother... I didn't understood why the back tick trick didn't work in my way, but now it is not completely clear ;-) but I got your solution, thanks.

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