I have a dataframe named df, just as below.

ID HHmm
1  0840
2  0910
3  1050
4  1210
5  1230

I want to add a third column, type, that follows these rules:

  for (k in 1 : nrow(df)){
    if(df$HHmm >= 0860 & df$HHmm <= 1060){
      df[k, 'type'] = "r1"
    }else{
      df[k, 'type'] = "c"
    }
  }

but I get the warning:

In if (df$HHmm >= 0860 & df$HHmm <= 1060) { ... :
  the condition has length > 1 and only the first element will be used

and I got a undesirable results, just like below.

ID HHmm type
1  0840 r1
2  0910 r1
3  1050 r1
4  1210 r1
5  1230 r1

The desirable resultes should be like below

ID HHmm type
1  0840 c
2  0910 r1
3  1050 r1
4  1210 c
5  1230 c

Can anyone spot what's wrong here? How to compare HHmm time format data in if loop?

CodePudding user response：

You need to define the index k; e.g. df$HHmm[k].

  for (k in 1:nrow(df)){
    if(df$HHmm[k] >= 0860 & df$HHmm[k] <= 1060){
      df[k, 'type'] = "r1"
    }else{
      df[k, 'type'] = "c"
    }
  }

CodePudding user response：

You do not need to (and should not) use a loop to do this kind of operation in R. It is slower, more verbose and harder to comprehend.

You just want to create a column called type with the value "c" and then assign the value "r1" to the subset of the column that meets your condition:

df$type  <- "c"
df$type[df$HHmm >= 0860 & df$HHmm <= 1060]  <- "r1"
df

# Output
#   ID HHmm type
# 1  1  840    c
# 2  2  910   r1
# 3  3 1050   r1
# 4  4 1210    c
# 5  5 1230    c