[R] Question with "apply"

[David Carlson]

The apply() function works on an array or a matrix. There is no need to
guess, just read the manual page:

? apply

So including a character variable forces the entire matrix to characters.
Excluding character variables will let you operate on the numeric values,
but your code suggests you are trying to create a new variable based on a
single column so apply() is the wrong tool. Without a working example, it is
not possible to be more specific. Including a sample of your data.frame with
dput() would make that possible.

-------------------------------------
David L Carlson
Associate Professor of Anthropology
Texas A&M University
College Station, TX 77840-4352


-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of Pooya Lalehzari
Sent: Thursday, May 9, 2013 10:51 AM
To: r-help at r-project.org
Subject: [R] Question with "apply"

Hello,
When I use "apply" on a data frame, it seems like I get an error when I have
a column that is not numeric. Via trial and error I realized that if I
remove that column, I can get it to run. Is there a better way to tell the
function not to worry about the character columns, especially since I am not
even trying to do any calculations on it?
R_Cat is the character column that is causing error and I am trying to do
calculations on t5R.

Data_F_Cat$t5R_Cat = apply(Data_F[,names(Data_F) != "R_Cat"],1,function(row)
{
    ifelse( abs(row["t5R"]) <Thresh1, 0,
    ifelse( abs(row["t5R"]) <Thresh2, ifelse( row["t5R"] <0, -1, 1),
    ifelse( abs(row["t5R"]) <Thresh3, ifelse( row["t5R"] <0, -2, 2),
    ifelse( abs(row["t5R"]) <Thresh4, ifelse( row["t5R"] <0, -3, 3),
    ifelse( abs(row["t5R"]) <0, -4, 4)))))
})


Thank you,
Pooya.


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