To calculate quantiles by group in R, you can use **quantile()** function from **dplyr** package.

The following method shows how you can do it with syntax.

**Method: Use quantile() Function**

```
library(dplyr)
df %>%
group_by(column1) %>%
summarize(quant25 = quantile(column2, 0.25,
quant50 = quantile(column2, 0.50),
quant75 = quantile(column2, 0.75),
quant100 = quantile(column2, 1.0))
```

The following example shows how to calculate quantile values by group in R.

## Using quantile() Function

Let’s see how we can calculate quantile values of column of of data frame:

```
# Load library
library(dplyr)
# Create data frame
df <- data.frame(Machine_name=c("A","B","A","C","D","B","C","D","D","C","A","B","B","C","D","D"),
Pressure=c(12.39,11.25,12.15,13.48,13.78,12.89,12.21,12.58,11.25,11.69,78.96,14.52,14.56,11.23,12.36,12.85),
Temperature=c(78,89,85,84,81,79,77,85,77,78,75,74,71,79,76,78),
Humidity=c(5,7,1,2,7,8,9,4,5,1,3,4,7,8,9,5))
# Define quantiles of interest
q = c(.25, .5, .75, 1)
# Calculate quantiles by grouping Machine_name
df %>%
group_by(Machine_name) %>%
summarize(quant25 = quantile(Pressure, probs = q[1]),
quant50 = quantile(Pressure, probs = q[2]),
quant75 = quantile(Pressure, probs = q[3]),
quant100 = quantile(Pressure, probs = q[4]))
```

Output:

```
Machine_name quant25 quant50 quant75 quant100
<chr> <dbl> <dbl> <dbl> <dbl>
1 A 12.3 12.4 45.7 79.0
2 B 12.5 13.7 14.5 14.6
3 C 11.6 12.0 12.5 13.5
4 D 12.4 12.6 12.8 13.8
```

The output shows quantile values for **Pressure** column which group by **Machine_name** column of data frame.