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rsubsethistogram
Lucas
Lucas

Reputation: 589

error subsetting data frame for plot purposes in R

I have a data frame which I can not reproduce and with the columns [col1,col2,...] being numeric values. When I try to plot one of the columns:

hist(df[,"col1"])

I get the following error:

Error in hist.default(df[, var]) : 'x' must be numeric*

But I can plot it when subsetting the data frame like this:

hist(df$col1]

This is not happening when plotting a boxplot

Upvotes: 0

Views: 1200

Answers (2)

akrun
akrun

Reputation: 886938

If it is a tibble, we can also use $

hist(df$mpg)

Upvotes: 0

Ronak Shah
Ronak Shah

Reputation: 388807

Mostly probably your df is not dataframe but a tibble.

When you subset a dataframe with one-colum you get a vector back.

mtcars[, 'mpg']
[1] 21.0 21.0 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 17.8 16.4 17.3 15.2 10.4 10.4
[17] 14.7 32.4 30.4 33.9 21.5 15.5 15.2 13.3 19.2 27.3 26.0 30.4 15.8 19.7 15.0 21.4

This works fine with hist :

hist(mtcars[,"mpg"])

which is same as doing

hist(mtcars$mpg)

But if you have a tibble, subsetting tibble by one-column returns a tibble back.

df <- tibble::tibble(mtcars)
df[,"mpg"]

# A tibble: 32 x 1
#     mpg
#   <dbl>
# 1  21  
# 2  21  
# 3  22.8
# 4  21.4
# 5  18.7
# 6  18.1
# 7  14.3
# 8  24.4
# 9  22.8
#10  19.2
# … with 22 more rows

So you get the error :

hist(df[,"mpg"])

Error in hist.default(df[, "mpg"]) : 'x' must be numeric

In which case you should use [[ to get a vector/

hist(df[["mpg"]])

Upvotes: 1

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