CODEWITHSUNDEEP
rreplacefilter
WayToNinja
WayToNinja

Reputation: 285

Replace certain value in R Failed

I was trying to replace values >= 4 in column cnt1 with ">4"

   date         cnt1  cnt2  cnt3    cnt4
  2014-01        3    0     0         1
  2014-01        5    0     0         2
  2014-01        8    3     0         4
  2014-01       32   29     0        30
  2014-01        3    3     0         3   
  2014-01        1    1     0         1
  2014-01        1    1     0         1

My code goes like this:

output$cnt1[output$cnt1>= "4"] <- ">=4"

And the result is like below:

date             cnt1  cnt2  cnt3    cnt4
      2014-01        3    0     0         1
      2014-01       >4    0     0         2
      2014-01       >4    3     0         4
      2014-01       32   29     0        30
      2014-01        3    3     0         3   
      2014-01        1    1     0         1
      2014-01        1    1     0         1

So it turns out that some values were not replaced.... Did I do something wrong? The Str of the data:

 $ cnt1: chr  "1" "1" "2" "2" ...
 $ cnt2: chr  "1" "1" "1" "0" ...
 $ cnt3: chr  "0" "0" "0" "0" ...
 $ cnt4: int  1 1 1 1 1 1 5 4 1 1 ...

Thanks

Upvotes: 0

Views: 100

Answers (1)

aeongrail
aeongrail

Reputation: 1384

As @thelatemail pointed out in comments you aren't comparing the same thing

Imagine that instead of comparing comething as being greater than 4, you compared something as being greater than "blah"

Is 5 > "blah" ? (is an integer greater than a string)

You want to compare integers with integers.

output$cnt1[output$cnt1 >= 4]

Not

output$cnt1[output$cnt1>= "4"]

As well as that, when you replace the values with ">4" all the other values in that column will be converted from a numeric type to a character type. This may or may not be what you are wanting

Edit:

When comparing strings you will get peculiar results. R does comparison this way whereby it looks at each character converts it to it's asci values, and then compares ascii value by ascii value

Consider:

> "a">"b"
[1] FALSE
> 
> "b"> "a"
[1] TRUE
> 
> "3">"4"
[1] FALSE
> 
> "5">"4"
[1] TRUE
> 
> "53">"4"
[1] TRUE
> 
> "35">"4"
[1] FALSE
> "alpha">"alphb"
[1] FALSE

If you translate each expressions into their corresponding ascii values; it all follows

Upvotes: 2

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