Thanks for the response David.
On Tue, Aug 16, 2011 at 1:13 PM, David Winsemius <dwinsem...@comcast.net> wrote:
>
> On Aug 16, 2011, at 3:37 PM, Sam Albers wrote:
>
>> ## Hello there,
>> ## I have an issue where I need to use the value of column names to
>> multiply with the individual values in a column and I have many
>> columns to do this over. I have data like this where the column names
>> are numbers:
>>
>> mydf <- data.frame(`2.72`=runif(20, 0, 125),
>> `3.2`=runif(20, 50, 75),
>> `3.78`=runif(20, 0, 100),
>> yy= head(letters,2), check.names=FALSE)
>
>> mydf
> 2.72 3.2 3.78 yy
> 1 31.07874 74.48555 89.306591 a
> 2 123.68290 74.30030 11.943576 b
> 3 89.64024 68.26378 97.627211 a
> 4 81.46604 59.79607 91.005217 b
>
>>
>> ## I had been doing something like this but this seems rather tedious
>> and clunky. These append the correct values to my dataframe but is
>> there any way that I can do this generally over each column, also
>> using each column name as the multiplier for that column?
>>
>> mydf$vd2.72 <- mydf$'2.72'*2.72
>> mydf$vd3.2 <- mydf$'3.2'*3.2
>> mydf$vd3.78 <- mydf$'3.78'*3.78
>>
>> ## So can I get to this point with a more generalized solution? For
>> now, I would also prefer to keep this in wide format and I am aware
>> (thanks to the list!) that I could use melt() to get the values I
>> want.
>
> You will get the warning that last last column is not "going right" but
> otherwise this returns what you asked for:
>
> sapply(1:length(mydf), function(i) mydf[[i]]* as.numeric(names(mydf)[i]) )
This suits my purposes well with a couple slight modifications:
## I made this into a data.frame so I could append it to the other one (mydf)
mydf.vd <- as.data.frame(sapply(1:length(mydf), function(i)
mydf[[i]]*as.numeric(names(mydf)[i]) ))
## I also renamed all the columns accordingly.
colnames(mydf.vd) <- paste("vd",names(mydf), sep="")
##Then added the new data.frame to the old one.
out <- cbind(mydf,mydf.vd)
Thanks for your help with this! (Also thanks Bert for the other
helpful suggestion)
> [,1] [,2] [,3] [,4]
> [1,] 84.53416 238.3538 337.57891 NA
> [2,] 336.41748 237.7610 45.14672 NA
> [3,] 243.82145 218.4441 369.03086 NA
> [4,] 221.58762 191.3474 343.99972 NA
> [5,] 81.78911 213.0770 97.90072 NA
> snipped remainder
>
> --
>
> David Winsemius, MD
> West Hartford, CT
>
>
Sam
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