Change type of column into numeric? [duplicate]

Question

I am working on the below data:

 r

  V1 V2 V3 V4 V5

1  C  1  1  0 16

2  A  1  1 16  0

3  A  1  1 16  0

class(r)

[1] "data.frame"

class(r[,2])

character

I have changed 2nd column into numeric using the code below:

as.numeric(r[,2])->r[,2]

as.numeric(r[,3])->r[,3]

as.numeric(r[,4])->r[,4]

as.numeric(r[,5])->r[,5]

Can I change it with only one statement?

Answer 1

Use lappy to convert the columns which you want to convert.

r

#   V1 V2 V3 V4 V5

# 1  C  1  1  0 16

# 2  A  1  1 16  0

# 3  A  1  1 16  0

str(r)

# 'data.frame':  3 obs. of  5 variables:

#  $ V1: chr  "C" "A" "A"

#  $ V2: chr  "1" "1" "1"

#  $ V3: chr  "1" "1" "1"

#  $ V4: chr  "0" "16" "16"

#  $ V5: chr  "16" "0" "0"

Here is the code to convert all columns except the first to numeric.

r[-1] <- lapply(r[-1], as.numeric)

r

#   V1 V2 V3 V4 V5

# 1  C  1  1  0 16

# 2  A  1  1 16  0

# 3  A  1  1 16  0

str(r)

# 'data.frame': 3 obs. of  5 variables:

#  $ V1: chr  "C" "A" "A"

#  $ V2: num  1 1 1

#  $ V3: num  1 1 1

#  $ V4: num  0 16 16

#  $ V5: num  16 0 0

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