CODEWITHSUNDEEP
r
user2113692
user2113692

Reputation: 131

How to multiply a single column in a data.frame by a number

I would like to know how to muliply a single column by 5 from a txt file that I used a script to read. I only know how to mulitply all of the columns by a number, but not a single column. This is my script for reading the txt file:

d = read.table(file="tst1.txt",header=TRUE)

Upvotes: 13

Views: 71384

Answers (2)

Oscar de León
Oscar de León

Reputation: 2361

Lets suppose your dataframe d has a column named "number" (you can see the actual names of the columns in the dataframe using str(d)). To multiply the column "number" by 5, use:

# You are referring to the column "number" within the dataframe "d"
d$number * 5

# The last command only shoes the multiplication.

# If you want to replace the original values, use
d$number <- d$number * 5

# If you want to save the new values in a new column, use
d$numberX5 <- d$number * 5

Also, try referring to the standard R documentation, which you can find in the official page.

Upvotes: 21

Jouni Helske
Jouni Helske

Reputation: 6477

d[,i]<-d[,i]*5. See ?Extract for more information about extracting parts of objects.

Upvotes: 5

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