[R] preserve class in apply function

[Naresh Gurbuxani]

Thanks for all the responses.  I need to use some text columns to determine method applied to numeric columns. 

Split seems to be the way to go.

Sent from my iPhone

> On Feb 7, 2023, at 8:31 AM, PIKAL Petr <petr.pikal using precheza.cz> wrote:
> 
> Hi Naresh
> 
> If you wanted to automate the function a bit you can use sapply to find
> numeric columns
> ind <- sapply(mydf, is.numeric)
> 
> and use it in apply construct
> apply(mydf[,ind], 1, function(row) sum(row))
> [1]  2.13002569  0.63305300  1.48420429  0.13523859  1.17515873 -0.98531131
> [7]  0.47044467  0.23914494  0.26504430  0.02037657
> 
> Cheers
> Petr
> 
>> -----Original Message-----
>> From: R-help <r-help-bounces using r-project.org> On Behalf Of Naresh Gurbuxani
>> Sent: Tuesday, February 7, 2023 1:52 PM
>> To: r-help using r-project.org
>> Subject: [R] preserve class in apply function
>> 
>> 
>>> Consider a data.frame whose different columns have numeric, character,
>>> and factor data.  In apply function, R seems to pass all elements of a
>>> row as character.  Is it possible to preserve numeric class?
>>> 
>>>> mydf <- data.frame(x = rnorm(10), y = runif(10))
>>>> apply(mydf, 1, function(row) {row["x"] + row["y"]})
>>> [1]  0.60150197 -0.74201827  0.80476392 -0.59729280 -0.02980335
>> 0.31351909
>>> [7] -0.63575990  0.22670658  0.55696314  0.39587314
>>>> mydf[, "z"] <- sample(letters[1:3], 10, replace = TRUE)
>>>> apply(mydf, 1, function(row) {row["x"] + row["y"]})
>>> Error in row["x"] + row["y"] (from #1) : non-numeric argument to binary
>> operator
>>>> apply(mydf, 1, function(row) {as.numeric(row["x"]) +
>> as.numeric(row["y"])})
>>> [1]  0.60150194 -0.74201826  0.80476394 -0.59729282 -0.02980338
>> 0.31351912
>>> [7] -0.63575991  0.22670663  0.55696309  0.39587311
>>>> apply(mydf[,c("x", "y")], 1, function(row) {row["x"] + row["y"]})
>>> [1]  0.60150197 -0.74201827  0.80476392 -0.59729280 -0.02980335
>> 0.31351909
>>> [7] -0.63575990  0.22670658  0.55696314  0.39587314
>> 
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