Change decimal digits for data frame column in R

Question

Questions about displaying of certain numbers of digits have been posted, however, just for single values or vectors, so I hope someone can help me with this.

I have a data frame with several columns and want to display all values in one column with two decimal digits (this column only). I have tried round() and format() and options(digits) but none worked on a column (numerical). I wonder if there is a method to do this without going the extra way of converting the column to a vector and gluing all together again.

Thanks a lot!

Answer 1

Here's an example of how to do this with the cars data.frame that comes installed with R.

First I'll add some variability so that we have numbers with decimal places:

data=cars+runif(nrow(cars))

Then to round just a single column (in this case the dist column to 2 decimal places):

data[,'dist']=round(data[,'dist'],2)

If your data contain whole numbers then you can guarantee that all values will have 2 decimal places by using:

cars[,'dist']=format(round(cars[,'dist'],2),nsmall=2)