[R] preserve class in apply function

[PIKAL Petr]

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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