Illogical result from an ifelse function

Asked Jun 11 '20 at 14:03

Active Jun 11 '20 at 14:03

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I have a column from a matrix like this:

 Mat[,1]
   1    2    3    4    5    6    7    8    9   10   11   12   13   14   15   16   17   18   19   20   21   22   23   24   25 
"89" "89"  "2" "87" "77"  "6" "89" "89" "89" "88" "83" "81"  "2" "89" "89" "19" "81" "82" "88" "89" "85" "82" "74" "87"  "5" 
  26   27   28   29   30   31   32   33   34   35   36   37   38   39   40   41   42   43   44   45   46   47   48 
 "3" "89" "17" "71" "89" "88" "88" "88" "77" "75" "46"  "0" "81" "88" "89"  "0" "89" "89" "89" "89"  "0"  "5"  "9"

And I want to apply the following function:

ifelse(Mat1[,1]>=40,1,0)

And the output is like this:

 1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 
 1  1  0  1  1  1  1  1  1  1  1  1  0  1  1  0  1  1  1  1  1  1  1  1  1  0  1  0  1  1  1  1  1  1  1  1  0  1  1  1  0  1 
43 44 45 46 47 48 
 1  1  1  0  1  1

Numbers 6, 25 and 47 are wrong. I cannot understad why. Can you help me?

asked Jun 11 '20 at 14:03

Carpa

2

Can you confirm that `class(Mat1)` returns `[1] "matrix" "array" `? Why are you comparing (what looks like) characters with a number? – Roland Jun 11 '20 at 14:07
4

Compare `as.integer("6") > 40` to `"6" > 40` – markus Jun 11 '20 at 14:08
2

@Henry That's not possible. A matrix cannot contain factors. – Roland Jun 11 '20 at 14:08
Yes, Mat1 is a matrix – Carpa Jun 11 '20 at 14:09
But, it contains characters. Maybe is that the problem. – Carpa Jun 11 '20 at 14:10
@markus `as.character(1:42) > 40` is not what I expected. – Henry Jun 11 '20 at 14:10
5

OK, then `40` is coerced to `"40"` during the comparison and the comparison lexicographic. – Roland Jun 11 '20 at 14:10
I did what markus proposed. I got that: > as.integer("6")>40 [1] FALSE > "6">40 [1] TRUE – Carpa Jun 11 '20 at 14:12
The problem is solved. Thank you very much everyone. – Carpa Jun 11 '20 at 14:15
1

I changed characters to numeric. – Carpa Jun 11 '20 at 14:16
2

Related: [Why does “one” < 2 equal FALSE in R?](https://stackoverflow.com/questions/27005295/why-does-one-2-equal-false-in-r), and several **Linked** therein. – Henrik Jun 11 '20 at 14:24

Illogical result from an ifelse function

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