Hi Jean-Baptiste,
two points:
1) Your variable "df" is a *local* variable which you define in your
function myfunc(), so it is not known outside myfunc(). When you ask
is.data.frame(df), R looks at the global definition of df - which is the
density function of the F distribution. To make your function run
(especially interactively) will require a major rewrite.
2) Generally, using variable names that are already used as R objects
(like "df" in your example) is a bad idea. For an example of the
problems you can run into, see 1) above.
3) Loops are not "the R way". Depending on what you want to do with the
subset of your data.frame, you may want to do something like this:
x.df[substr(x.df$Code,1,1)=="R",]
Look at ?substr to learn more - this function is "vectorized", meaning
that it takes a vector input and returns a vector output. Look at
section 2.7 in "An introduction to R".
Good luck!
Stephan
Jean-Baptiste Combes schrieb:
Hello,
I use R 2.10, and I am new in R (I used to use SAS and lately Stata), I am
using XP.
I have a data which has a data.frame format called x.df (read from a csv
file). I want to take from this data observations for which the variable
"Code" starts with an "R". I took all the Code and put them into a vector
vec<-grep("R[A-Z][A-Z]",x.df$Code,value=TRUE)
Then I created a function that is supposed to take all the lines in the my
data x.df for which "Code" equals one value of "vec". See the code below
where I created a loop to do that.
myfunc<-function(data,var2,var1)
+ {
+ i=1
+ while (i<632){
+ line<-subset(data,var2==var1[i])
+ if (i==1){
+ df<-line
+ df<-data.frame(df)
+ }
+ else {
+ line<-data.frame(line)
+ df<-rbind(df,line)
+ }
+ i<-i+1
+ }
+ fix(df)
+ }
The results of my program higly depend on the few last lines of the program.
If I put "fix(df)", as above, the function opens a window with my data and
it seems a sensible results (I have not checked in details but I barely have
what I am suppose to get).
myfunc<-function(data,var2,var1)
...
+ }
+ df<-data.frame(df)
+ print(is.data.frame(df))
+ }
myfunc(x.df,x.df$Code,vec)
[1] TRUE
print(is.data.frame(df))
[1] FALSE
In the case above I ask whether or not the "df" is a data.frame and the
answer is true, when the program has ended, I ask again and the answer is
false.
Could anyone tell me what to do to get this data and could anyone tell me
why those differences in the results?
as.data.frame(df)
Erreur dans as.data.frame.default(df) :
impossible de convertir automatiquement la classe "function" en un
tableau de données (data.frame)
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