[R] Odp: nesting multiple for loops

From: Petr PIKAL <petr.pikal_at_precheza.cz>
Date: Fri, 15 Apr 2011 12:18:54 +0200

Hi

r-help-bounces_at_r-project.org napsal dne 15.04.2011 01:34:22:

> Hi everyone.
>
> I am quite frustrated that this doesn't work, as all the functions
within
> work fine by themselves. I'd also like any pointers to how to avoid
'for'
> loops in my code. I understand it's less than desirable, but I'm still
quite
> new and use them a lot.
>
> I have a few wide datasets (90 to 120) with long column names, each name
> contains a number of different 'markers'. Each could be considered a
factor
> variable within the column name. Their are two categories of factors,
we'll
> call them f1 and f2.
>
> The data frame names look something like this:
> 'ace_van' , 'boy_van', 'car_xes' , 'ace_xes', 'dog_wall' , 'car_zounds'
>
> f1 <- c('ace', 'boy', 'car', 'dog')
> f2 <- c('van', 'wall', 'xes', 'zounds') # actual vectors are length 6
and
> 7, so I don't want to individually sum the 42 combinations.
>
> > var.table <- function(data, vec1, vec2)
> {
> table <- as.data.frame(matrix(nrow = length(vec1), ncol =
length(vec2)),
> row.names = vec1)
> names(table) <- vec2
> for (i in 1:length(vec1))
> {
> for (j in 1:length(vec2))
> {
> indices <- intersect(grep(vec1[j], names(data), value = TRUE),
> grep(cats[i], names(data), value = TRUE))
> table[i,j] <- sum(data[ ,indices])
> }
> }
> table
> }
>
> > var.table(mydf, f1, f2)
>
> Output:
>
> Error in FUN(X[[1L]], ...) :
> only defined on a data frame with all numeric variables
>
>
> Every entry in mydf is an integer with no missing values.

I can not provide solution as I can not decipher what you want to do but here are few comments.

Do not use names of functions for naming objects e.g. table, it can be quite confusing.
What is cats??
Are you sure that mydf values are numbers?

What does str(mydf) say?

Do I understand that you want summarise all values in columns of data frame that have some common name?

lapply(f2, grep, names(mydf))

will give you list of indices of columns in mydf matching particular f2 item. From this you can continue. Maybe plyr package can also be used.

Regards

Petr

>
> Thanks a ton.
>
> -Ben
>
> [[alternative HTML version deleted]]
>
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