[R] Odd behavior of a function within apply

[John Fox]

Dear Erin,

The problem is that the data frame gets coerced to a character matrix, 
and the only column with "" entries is the 9th (the second one you 
supplied):

as.matrix(test1.df)
    X1_1_HZP1 X1_1_HBM1_mon X1_1_HBM1_yr
1  "48160"   "December"    "2014"
2  "48198"   "June"        "2018"
3  "80027"   "August"      "2016"
4  "48161"   ""            NA
5  NA        ""            NA
6  "48911"   "August"      "1985"
7  NA        "April"       "2019"
8  "48197"   "February"    "1993"
9  "48021"   ""            NA
10 "11355"   "December"    "1990"

(Here, test1.df only contains the three columns you provided.)

A solution is to use sapply:

 > sapply(test1.df, count1a)
     X1_1_HZP1 X1_1_HBM1_mon  X1_1_HBM1_yr
             2             3             3


I hope this helps,
  John


On 2022-08-08 1:22 p.m., Erin Hodgess wrote:
> Hello!
> 
> I have the following data.frame
>   dput(test1.df[1:10,8:10])
> structure(list(X1_1_HZP1 = c(48160L, 48198L, 80027L, 48161L,
> NA, 48911L, NA, 48197L, 48021L, 11355L), X1_1_HBM1_mon = c("December",
> "June", "August", "", "", "August", "April", "February", "",
> "December"), X1_1_HBM1_yr = c(2014L, 2018L, 2016L, NA, NA, 1985L,
> 2019L, 1993L, NA, 1990L)), row.names = c(NA, 10L), class = "data.frame")
> 
> And the following function:
>> dput(count1a)
> function (x)
> {
>      if (typeof(x) == "integer")
>          y <- sum(is.na(x))
>      if (typeof(x) == "character")
>          y <- sum(x == "")
>      return(y)
> }
> When I use the apply function with count1a, I get the following:
>   apply(test1.df[1:10,8:10],2,count1a)
>      X1_1_HZP1 X1_1_HBM1_mon  X1_1_HBM1_yr
>             NA             3            NA
> However, when I do use columns 8 and 10, I get the correct response:
>   apply(test1.df[1:10,c(8,10)],2,count1a)
>     X1_1_HZP1 X1_1_HBM1_yr
>             2            3
>>
> I am really baffled.  If I use count1a on a single column, it works fine.
> 
> Any suggestions much appreciated.
> Thanks,
> Sincerely,
> Erin
> 
> 
> Erin Hodgess, PhD
> mailto: erinm.hodgess using gmail.com
> 
> 	[[alternative HTML version deleted]]
> 
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-- 
John Fox, Professor Emeritus
McMaster University
Hamilton, Ontario, Canada
web: https://socialsciences.mcmaster.ca/jfox/