[R] "text"-function: adding text in an x,y-plot

[Uwe Ligges]

Helmut Kudrnovsky wrote:

> Hello R-friends,
> 
> i have a question to the "text"-function.
> 
> a little test-dataset for better understanding:
> 
> -the dataset was imported with read.table(....,header=TRUE)
> s1-s10 are the samplenames
> 
>     var1 var2 var3
> s1     1    1    2
> s2     2    3    1
> s3     2    2    3
> s4     5    4    3
> s5     4    2    3
> s6     6    3    2
> s7     8    5    4
> s8     7    2    1
> s9     9    3    2
> s10    8    6    4
> 
> -then i´ve performed a pincipal component analysis with prcomp
> 
> -for displaying the result in a x,y-graph i transformed out.pca$x into 
> the dataframe points
>  points <- out.pca$x
>  > points
>            PC1         PC2        PC3
> s1  -4.7055777 -0.14781544 -0.3683602
> s2  -3.1854599  0.19661476  1.5212455
> s3  -3.2687980  0.78193513 -0.6352458
> s4   0.2278948  1.00061498  0.2164108
> s5  -1.4382847  0.02500633 -0.9114340
> s6   0.6216283 -0.68606440  0.2071083
> s7   3.4951878  1.17343675 -0.3266629
> s8   1.0153619 -2.37274378  0.1978058
> s9   3.3673983 -1.82145761 -0.2071739
> s10  3.8706492  1.85047328  0.3063065
> 
> - with plot(points$PC1, points$PC2, type="n") i start a graph without 
> displaying anything at the x,y-coordinates

I think points should be a matrix rather than a list or data.frame, 
hence the code above won't work. Instead:


  plot(points[,"PC1"], points[,"PC2"], type="n")


> - i want now to display the samplenames at the right x,y-coordinate;  i 
> generated a dataframe called lab with the samplenames
> 
>  > lab
>     V1
> 1   s1
> 2   s2
> 3   s3
> 4   s4
> 5   s5
> 6   s6
> 7   s7
> 8   s8
> 9   s9
> 10 s10
> 
> - i´ve studied the "text"-helppage and so i tried the following:
> text(pca$PC1, pca$PC2, labels=lab)

Hmm, what is pca ???


  lab <- rownames(points)
  text(points[,"PC1"], points[,"PC2"], labels=lab)

works for me.


> - in the plot there is now c(1,3,4,5,6,7,8,9,10,2) displayed instead of 
> s1-s10

Quite probably you lab was a *factor* ...


> is out there any idea what i'am doing wrong? is there maybe another way 
> of displaying the samplenames at the right x,y-coordinate?

We cannot say what you did wrong when constructing your plot, but we 
know that your descibtion above is wrong, because it does not even work 
to generate the empty plot the way ...

Please read the posting guide and rethink at least one time whether the 
code you are giving us is reproducible. Your code was not.

Uwe Ligges



> greetings from the sunny tirol with thanks in advance
> helli
> 
> platform i386-pc-mingw32
> arch     i386
> os       mingw32 - win xp
> system   i386, mingw32
> status
> major    2
> minor    1.0
> year     2005
> month    04
> day      18
> language R
> 
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