[R] How to transfer variable names to column names?

[Dennis Murphy]

Hi:

Using Michael's example data, here's another approach:

x = data.frame(x = 1:5)
y = data.frame(y = 1:10)
z = data.frame(z = 1:3)

# Generate a vector to name the list components
nms <- c('x', 'y', 'z')
# Combine data frames into a list
L <- list(x, y, z)
# name them
names(L) <- nms
# Use lapply() to get the number of rows in each component data frame
as.data.frame(lapply(L, nrow))
  x  y z
1 5 10 3

HTH,
Dennis

On Tue, Sep 20, 2011 at 11:23 AM, Vining, Kelly
<Kelly.Vining at oregonstate.edu> wrote:
> Hello R users,
> I have a set of data frames for which I am tallying row numbers, as shown below.
>
>> nrow(mC_Explant)
> [1] 14480
>> nrow(mC_Callus)
> [1] 23320
>> nrow(mC_RegenPlant)
> [1] 8108
>
> etc.
>
> I want to create a new data frame which has the variable names as column headings, and then a single row with the nrow tallies. My first step was this:
>
> dfIntron <- c(nrow(mC_Explant), nrow(mC_Callus), nrow(mC_RegenPlant))
>
> Then, to set the column names, I tried this, and got the following error:
>
>  colnames(dfIntron) <- c("mC_Explant", "mC_Callus", "mC_RegenPlant")
> Error in `colnames<-`(`*tmp*`, value = c("mC_Explant", "mC_Callus", "mC_RegenPlant" :
>  attempt to set colnames on object with less than two dimensions
>
> Even my first step seems wildly inefficient, and obviously doesn't work. There must be a simple way to do this, but I can't use table(), for example, as there are multiple data frames.
>
> Any help will be appreciated.
>
> --Kelly V.
>
>
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