Why does x axis label show df[,1] and not the column names?

Question

I am trying to get histograms of all columns of a data frame isNumVal using sapply. Codes below:

sapply(isNumVal, plotHist)

plotHist <- function(df){
          df <- tbl_df(df)

            print(
              ggplot(df, aes(x = df[1])) + geom_histogram() 
            )

          }

The x axis label in all the plots is showing df1.

How do i get it show the name of the columns?

Hi useR. its not working. ggplot is substituting "value" in place of "df[,1] in all plots with your code. — Ravi Shankar Hela, Jun 18 '18 at 13:53
Because `df[1]` is what you assigned to x, not whatever the column is called — camille, Jun 18 '18 at 13:54
It's also well documented that using the name of the data frame inside `aes` will often introduce errors and scoping issues. You can use a tidyeval approach, or there are other SO questions that will help programmatically create ggplots — camille, Jun 18 '18 at 13:56
Possible duplicate of [using an apply function with ggplot2 to create bar plots for more than one variable in a data.frame](https://stackoverflow.com/questions/41895513/using-an-apply-function-with-ggplot2-to-create-bar-plots-for-more-than-one-varia) — camille, Jun 18 '18 at 14:03
Add `+ xlab(lab name )` after your `geom_histogram( )` call as in http://ggplot2.tidyverse.org/reference/labs.html. Also see the example to properly write the `(aes())` function as pointed out by @camille — Andrew, Jun 18 '18 at 14:20

score 0 · Answer 1 · answered Jun 18 '18 at 15:31

0

There are many other ways, here is one. Try to pass dataframe and the column name to your function, and use aes_string:

plotHist <- function(myDf, myCol){
  ggplot(myDf, aes_string(x = myCol)) + geom_histogram()
}

lapply(colnames(isNumVal), function(i) plotHist(isNumVal, i))

answered Jun 18 '18 at 15:31

zx8754

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thank you zx. It works. Can you point me to some reading to understand why my original code doesn't work. – Ravi Shankar Hela Jun 19 '18 at 12:08
@RaviShankarHela Sorry, don't understand your question? – zx8754 Jun 19 '18 at 12:24
What is wrong with the code below: sapply(isNumVal, plotHist) plotHist <- function(df){ df <- tbl_df(df) print( ggplot(df, aes(x = df[1])) + geom_histogram() ) } – Ravi Shankar Hela Jun 19 '18 at 16:10
@RaviShankarHela as explained by other in the comments, you are losing the names of your dataframe when subsetting. In `functoin(df)`, the `df` is a unnamed vector, that you are converting to a dataframe, which you again subsetting using `df[1]`. – zx8754 Jun 19 '18 at 21:02
Got it. Thank you all! – Ravi Shankar Hela Jun 20 '18 at 01:38

Why does x axis label show df[,1] and not the column names?

1 Answers1