[R] Problems with aggregate

From: Mcmahon, Kevin <kwyatt.mcmahon_at_ttuhsc.edu>
Date: Thu, 21 Feb 2008 15:47:53 -0600

Hello list,  

I'm new to this list, so please forgive my ignorance. I have searched R-help for some hints into what might be my problem, but I truly have no idea where to go from here.  

I have an object of approximately 15,000 rows and 2 columns. There are many duplicates in the first column, all with different corresponding values in the second column. For example (2 is duplicated):

2 3.2

15 1.2

2 8.4

8 9.2

7 0.4  

I used the following code to aggregate these based on the first column and get the min and max:

min<-aggregate(as.numeric(humanneph[,2]), list(as.numeric(humanneph[,1])), min)

max<-aggregate(as.numeric(humanneph[,2]), list(as.numeric(humanneph[,1])), max)  

Both worked beautifully!  

THEN, I accidentally overwrote the object min. Since I hadn't touched the object humanneph, I copied the above code from my saved history and re-ran it. I get the following error:

Error in FUN(X[[1L]], ...) : argument "INDEX" is missing, with no default  

So, I went back and again, copying directly from my saved history, re-made my object humanneph, and re-ran the above code again. Still the same problem!!!  

So, it seems that after running this code once, suddenly aggregate does not work!!!  

Can anyone help me?  

My sessionInfo()

R version 2.5.1 (2007-06-27)


attached base packages:

[1] "stats" "graphics" "grDevices" "utils" "datasets"

[7] "base"



K. Wyatt McMahon, Ph.D.

Postdoctoral Research Associate

Department of Internal Medicine

Texas Tech University Health Sciences Center

Lubbock, TX



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