How to change factor columns to numeric columns

Question

I have a dataframe with factor columns and I need to change them to numeric.

head(IBOV)
          Date      Price       Open       High        Low  Vol. Change..
1 Oct 18, 2019 104,784.74 105,011.71 105,464.25 104,524.97 2.84M   -0.22%
2 Oct 17, 2019 105,015.77 105,388.63 105,891.19 104,826.61 4.19M   -0.39%
3 Oct 16, 2019 105,422.80 104,485.87 105,462.07 103,521.08 4.51M    0.89%
4 Oct 15, 2019 104,489.56 104,298.53 105,047.62 104,052.48 4.09M    0.18%
5 Oct 14, 2019 104,301.58 103,833.59 104,304.85 103,438.47 2.99M    0.45%
6 Oct 11, 2019 103,831.92 101,818.60 104,380.89 101,818.60 4.35M    1.98%

I tried to change column 2 to 5 with this code:

IBOV[ ,2:5] <- as.numeric(gsub(",", "", IBOV[ ,2:5]))

But it returns them all as NA's, and this message:

IBOV[ ,2:5] <- as.numeric(gsub(",", "", IBOV[ ,2:5])) Warning message: NAs introduced by coercion

head(IBOV) Date Price Open High Low Vol. Change.. 1 Oct 18, 2019 NA NA NA NA 2.84M -0.22% 2 Oct 17, 2019 NA NA NA NA 4.19M -0.39% 3 Oct 16, 2019 NA NA NA NA 4.51M 0.89% 4 Oct 15, 2019 NA NA NA NA 4.09M 0.18% 5 Oct 14, 2019 NA NA NA NA 2.99M 0.45% 6 Oct 11, 2019 NA NA NA NA 4.35M 1.98%

What am I doing wrong?

Duplicate of [How to convert a factor to integer\numeric without loss of information?](https://stackoverflow.com/questions/3418128/how-to-convert-a-factor-to-integer-numeric-without-loss-of-information) — M--, Oct 22 '19 at 19:27

score 0 · Accepted Answer · answered Oct 23 '19 at 06:54

Proceed like this:

Step 1: your data (in the absence of reproducible data, here's some mock data):

set.seed(12)
df <- data.frame(
  var1 = sample(1:10, 3),
  var2 = c("2,130.34", "1,000.01", "20,999.55"),
  var3 = c("23%", "-1.45%", "12.88%")
)
df
  var1      var2   var3
1    1  2,130.34    23%
2    8  1,000.01 -1.45%
3    9 20,999.55 12.88%

Step 2: str shows that you have two factors:

str(df)
'data.frame':   3 obs. of  3 variables:
 $ var1: int  1 8 9
 $ var2: Factor w/ 3 levels "1,000.01","2,130.34",..: 2 1 3
 $ var3: Factor w/ 3 levels "-1.45%","12.88%",..: 3 1 2

Step 3: convert factors to characters using lapply:

df[,2:3] <- lapply(df[,2:3], as.character)

Step 4: remove commas and percentage signs:

df[,2:3] <- lapply(df[,2:3], function(x) gsub(",|%", "", x))
df
  var1     var2  var3
1    1  2130.34    23
2    8  1000.01 -1.45
3    9 20999.55 12.88

Step 5: convert to numeric:

df[,2:3] <- lapply(df[,2:3], as.numeric)

Step 6: check conversion:

(str(df)
'data.frame':   3 obs. of  3 variables:
 $ var1: int  1 8 9
 $ var2: num  2130 1000 21000
 $ var3: num  23 -1.45 12.88

Thanks man, it worked. I was removing commas and percentage before transform the data into character. I believe that was My mistake. — Gabriel Meirelles, Oct 23 '19 at 14:58
Thanks for the thanks. It is customary on SO to express gratitude in the form of clicking the upward triangle on the left of the Answer box. — Chris Ruehlemann, Oct 24 '19 at 09:06

How to change factor columns to numeric columns

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