On Wed, 17 Mar 2010, Yong Wang wrote:
Dear List
I am getting a problem when using "eval(parse)".
Code below sketchs what I am trying to do:
For each row of a N*K dataframe (I use a 2*2 dataframe in the example below),
applying a number of functions and get the outputs (two functions,
"sum" and "var" are used in the example below).
The problem is eval(parse(text="sum(para)")) works fine but not when
"sum" is replaced by "var".
in the later case, a matrix instead of a number is returned.
Any suggestion highly appreciated.
Thank you
#===================================================The function
myloop <-function(datfra,funs) {
rows<-dim(datfra)[1];
totfunnum<-length(funs);
for (i in 1:rows) {
vec<-datfra[i,];
# I suggest:
browser()
# Now try print(vec), str(vec), etc till you understand
# why the results do not agree with your expectation
# HTH,
# Chuck
for(k in 1:totfunnum) {
print(funs[k]);
x<-eval(parse(text=funs[k]));
print(x);
}
}
}
#================================================Experiemental run
workport<-data.frame(matrix(1:4,2,2))
funs<-c("sum(vec,na.rm=T)","var(vec,na.rm=T)")
myloop(workport,funs)
#================================================ Outputs of the
Experimental run
[1] "sum(vec,na.rm=T)"
[1] 4
[1] "var(vec,na.rm=T)"
X1 X2
X1 NA NA
X2 NA NA
[1] "sum(vec,na.rm=T)"
[1] 6
[1] "var(vec,na.rm=T)"
X1 X2
X1 NA NA
X2 NA NA
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
E mailto:cbe...@tajo.ucsd.edu UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
