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R Percentiles
Percentiles
Percentiles used in mathematics to give you a number that describes the value that the given percentage is less than that.
If we look at the wt (weight) variable values from the mtcars data set:
Observation of wt (weight)
| 1.513 | 1.615 | 1.835 | 1.935 | 2.140 | 2.200 | 2.320 | 2.465 |
| 2.620 | 2.770 | 2.780 | 2.875 | 3.150 | 3.170 | 3.190 | 3.215 |
| 3.435 | 3.440 | 3.440 | 3.440 | 3.460 | 3.520 | 3.570 | 3.570 |
| 3.730 | 3.780 | 3.840 | 3.845 | 4.070 | 5.250 | 5.345 | 5.424 |
What is 75. motor weight percentile? The answer is 3.61 or 3 610 lbs, which means that 75% or cars weigh 3 310 lbs or less:
Example
Data_Cars <- mtcars
# c() specifies which percentile you want
quantile(Data_Cars$wt, c(0.75))
# c() specifies which percentile you want
quantile(Data_Cars$wt, c(0.75))
Result
75%
3.61
If you use a quantile() function without specifying a parameter c(), you will get 0, 25, 50, 75 and 100 percent:
Example
Data_Cars <- mtcars
quantile(Data_Cars$wt)
quantile(Data_Cars$wt)
Result
0% 25% 50% 75% 100%
1.51300 2.58125 3.32500 3.61000 5.42400
Quartiles
The quartiles are data divided into four parts, which are arranged in ascending order:
- The value of the first quartile cuts off the first 25% of the data
- The value of the second quartile cuts off the first 50% of the data
- The value of the third quartile cuts off the first 75% of the data
- The value of the fourth quartile cuts off the 100% of the data
Use the quantile() function to get the quartiles.