How to extract values of a dataframe based on a vector containing the row names of the dataframe?

Question

I have a data frame df, which is as follows. The left-hand side is the row names and the first column is the corresponding values.

              v1   
 a177:a1297  0.1
 a177:a842   0.2
 a177:a796   0.4
 a24:a1437   0.3
 a24:a1256   0.6
 a24:a762    0.7

I have a vector of characters which are the row names of df. The vector is dfnames

  str(dfnames)
  chr [1:5] "a177:a1297" "a177:a842" "a177:a796" "a24:a1437" "a24:a1256" "a24:a762"

If I extract one value based on a specific row name, it would be:

    df["a177:a1297",]
   [1]  0.1

Now I want to extract all the values of df based on dfnames

  df[dfnames,]
  [1] NA NA NA NA NA NA

Could anyone tell me how to extract the values of df based on a vector that contains the row names of df?

That's weird, it works for me. I get > df[dfnames, ] \n [1] 0.1 0.2 0.4 0.3 0.6 0.7 — Yannis Vassiliadis
– Yannis Vassiliadis, Commented Jun 8, 2017 at 20:53
Passing a string should work, please make your problem reproducible. Try this example: df1 <- mtcars[1:10, 1:3]; myRows <- c("Valiant", "Duster 360"); df1[myRows, ] — zx8754
– zx8754, Commented Jun 8, 2017 at 20:57
Possible duplicate: stackoverflow.com/questions/23652566/… — zx8754
– zx8754, Commented Jun 8, 2017 at 21:02

Bea · Accepted Answer · 2017-06-08 20:50:59Z

3

You can do:

df[which(row.names(df) %in% dfnames),]

answered Jun 8, 2017 at 20:50

Bea

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