can I select some rows in my data set whose have the same value in 2 of the columns?

Question

I have a data set with 40 columns and 2000 rows. the value of 2 columns are important. I want to select rows whose have the same value in these 2 columns. a small sample of my data is like this

2 3 4 5 6 3 23 32
4 3 4 1 0 5 6  43
4 4 3 22 1  2  23

Suppose I want to select rows whose have same value in first and third columns. So I want the second row to be stored in a new data set

@Sotos how this question is related to mine? she did not have same value in those columns — sherek_66, Jun 28 '19 at 14:51
@Sotos Could you plz tell me how I can delete those rows from main data set? — sherek_66, Jun 28 '19 at 14:59
Sorry. I just realised what you want to do. To drop the rows with same values just do `df[df[1] != df[3]]` — Sotos, Jun 28 '19 at 15:00
I get this error: Error in Ops.factor(left, right) : level sets of factors are different — sherek_66, Jun 28 '19 at 17:48
I forgot a comma. Also check the structure of your data frame. If you have factors convert them to numeric. `df[df[1] != df[2],]` — Sotos, Jun 28 '19 at 17:53
still gives me error, even when all factors are numeric: Error in Ops.factor(left, right) : level sets of factors are different — sherek_66, Jun 28 '19 at 19:42

score 1 · Accepted Answer · answered Jun 28 '19 at 21:42

I take from your comments that you have numbers stored as factors in that dataframe. Factors have different internal values. So when the console output shows the factor level to be 4 it is not necessarily a 4 in the internal representation. In general, two different factors are not compatible with each other except if they have the same level set. To see the 'internal representation' of your first column use as.numeric(df[[1]]).

Now to the solution of your problem. You first have to convert the factors in your columns 1 and 3 (or all columns) into numeric values using the factor levels. Instructions for that can be found here.

## converting factor levels to numeric values
df[[1]] <- as.numeric(levels(df[[1]]))[df[[1]]]
df[[3]] <- as.numeric(levels(df[[3]]))[df[[3]]]

## filter data
df[df[1] == df[3],]

can I select some rows in my data set whose have the same value in 2 of the columns?

1 Answers1