[R] Col names in a data frame

Jan T. Kim
Thu, 21 Jan 2021 21:44:38 -0000

it looks to me that the names are cranked through make.names for
data frames case while that doesn't happen for matrices. Peeking
into the `colnames<-` code supports this idea, but that in turn
uses `names<-` which is a primitive and so defies further easy
peeking.

The data.frame function provides the check.names parameter to
switch this on / off, but for other classes this checking doesn't
seem to be provided.

Perhaps the idea behind this discrepancy is to enable the use of
the $ operator to access columns of the data frame, while that's
not possible for matrices anyway. (Personally, I don't find the
results of make.names that useful, though, and I tend to sanitise
them myself when working with data frames with unwieldy column
names).

Best regards, Jan


On Thu, Jan 21, 2021 at 03:58:44PM -0500, Bernard McGarvey
wrote:
> Here is an example piece of code to illustrate an issue:
>
> rm(list=ls()) # Clear Workspace
> #
> Data1 <- matrix(data=rnorm(9,0,1),nrow=3,ncol=3)
> Colnames1 <- c("(A)","(B)","(C)")
> colnames(Data1) <- Colnames1
> print(Data1)
> DataFrame1 <- data.frame(Data1)
> print(DataFrame1)
> colnames(DataFrame1) <- Colnames1
> print(DataFrame1)
>
> The results I get are:
>
>             (A)        (B)        (C)
> [1,]  0.4739417  1.3138868  0.4262165
> [2,] -2.1288083  1.0333770  1.1543404
> [3,] -0.3401786 -0.7023236 -0.2336880
>         X.A.       X.B.       X.C.
> 1  0.4739417  1.3138868  0.4262165
> 2 -2.1288083  1.0333770  1.1543404
> 3 -0.3401786 -0.7023236 -0.2336880
>          (A)        (B)        (C)
> 1  0.4739417  1.3138868  0.4262165
> 2 -2.1288083  1.0333770  1.1543404
> 3 -0.3401786 -0.7023236 -0.2336880
>
> so that when I make the matrix with headings the parentheses are replaced
by periods but I can add them after creating the data frame and the column
headings are correct.
>
> Any ideas on why this occurs?
>
> Thanks
>
>
> Bernard McGarvey
> Director, Fort Myers Beach Lions Foundation, Inc.
> Retired (Lilly Engineering Fellow).
>
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