Applying if statement to data frame elements

Question

Here is what i am trying to do: 1. Read in csv file 2. Create a column number 107 and copy values from column 67 based on the condition:' only copy values if row values in column 70 is "Yes"'

Code:

report <- read.csv("C:\\Users\\ha317981\\Desktop\\practice\\input.csv",  header=1)
for(i in 1:length(report[[70]])-1){ 
    if(report[[i, 70]] =="Yes"){
      report[[i,107]] <-report[[i, 67]]  
    }
    i<- i + 1
  }

Error: Error in [[.default(col, i, exact = exact) : attempt to select less than one element in get1index

score 2 · Accepted Answer · edited Feb 18 '17 at 09:53

2

You can replace your code with the vectorised operation as below.

report[,107] <- ifelse(report[,70] == "Yes", report[,67], NA)

edited Feb 18 '17 at 09:53

Richard Telford

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answered Feb 17 '17 at 15:56

Karthik Arumugham

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score 2 · Answer 2 · answered Feb 17 '17 at 16:22

2

You could also use mutate from the dplyr package paired with ifelse.

From the documentation:

"Mutate adds new variables and preserves existing; transmute drops existing variables."

require(dplyr)
report <- read.csv("C:\\Users\\ha317981\\Desktop\\practice\\input.csv",  header=1)

# mutate(tbl_df, NewColumn = Value, ...)

newReport <- mutate(report, Col107 = ifelse(Col70 == "Yes", Col67, NA))

This will create a new variable in your (presumably?) data frame based on the values of Column 70, where the value will either be copied from Column 67 or NA.

answered Feb 17 '17 at 16:22

JJEO

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Thanks! :) . Could you also point out what is wrong with my code? – Harminder Puri Feb 18 '17 at 14:35
The problem is that your code is trying to create a new column line by line, rather than creating one column that's the same length as the other columns in one statement. Data frames in R need to have all of their columns be the same length (http://stackoverflow.com/questions/9253303/r-dataframe-with-varied-column-lengths). To fix this, you would have to add a column before the `for` loop and _then_ change it's values line by line. You could do this by putting `report$Col107 = NA` before your `for` loop. – JJEO Feb 18 '17 at 17:28

Applying if statement to data frame elements

2 Answers2