# Create Histogram With ggplot in R

1. Use `geom_histogram` to Create a Histogram With `ggplot` in R
2. Use `fill`, `colour` and `size` Parameters to Modify the Histogram Visuals in R
3. Use `facet_wrap` to Construct Multiple Histograms Grouped by Category in R

This article will demonstrate how to create a histogram with `ggplot` in R.

## Use `geom_histogram` to Create a Histogram With `ggplot` in R

A simple histogram is constructed using the `geom_histogram` function, and it only needs one variable to draw the graph. In this case, we use the `diamonds` data set, namely, the `price` column from it, to specify the mapping to the x-axis. `geom_histogram` automatically chooses the bin size and scale data points unless explicitly passed by the user.

``````library(ggplot2)

p1 <- ggplot(diamonds, aes(x = price)) +
geom_histogram()

p1
`````` The following example expands the previous code snippet to specify the breakpoints on each axis using `scale_x_continuous` and `scale_y_continuous` functions. `breaks` parameter is utilized to pass the values generated by `seq` function. `seq` parameters are intuitive to read as they form the pattern - `(from, to, by)`. We also utilize the `grid.arrange` function to display two graphs side-by-side for visual comparison.

``````library(ggplot2)
library(gridExtra)

p1 <- ggplot(diamonds, aes(x = price)) +
geom_histogram()

p2 <- ggplot(diamonds, aes(x = price)) +
geom_histogram() +
scale_y_continuous(breaks = seq(1000, 14000, 2000)) +
scale_x_continuous(breaks = seq(0, 18000, 2000))

grid.arrange(p1, p2, nrow = 2)
`````` ## Use `fill`, `colour` and `size` Parameters to Modify the Histogram Visuals in R

The common parameters such as `fill`, `colour` and `size` can be utilized to change the visual of graph bins. The `fill` parameter specifies the color by which bins are filled; in contrast, `colour` is used for the bin strokes. `size` takes numeric value to denote the width of the bin strokes. Notice also that the following code snippet adds the `name` parameter to both axes.

``````library(ggplot2)
library(gridExtra)

p3 <- ggplot(diamonds, aes(x = price)) +
geom_histogram(fill = "pink", colour = "brown") +
scale_y_continuous(breaks = seq(1000, 14000, 2000)) +
scale_x_continuous(breaks = seq(0, 18000, 2000))

p4 <- ggplot(diamonds, aes(x = price)) +
geom_histogram(fill = "pink", colour = "brown", size = .3) +
scale_y_continuous(breaks = seq(1000, 14000, 2000), name = "Number of diamonds" ) +
scale_x_continuous(breaks = seq(0, 18000, 2000), name = "Price" )

grid.arrange(p3, p4, nrow = 2)
`````` ## Use `facet_wrap` to Construct Multiple Histograms Grouped by Category in R

The `facet_wrap` function can be used to draw multiple histograms based on the set of variables. `diamonds` data set gives provides enough dimensions to choose the variables from one of its columns. E.g., we chose the `cut` column to display different `price` histograms for each type. The `theme` function can also be combined with the `geom_histogram` to specify custom formatting for graph elements.

``````library(ggplot2)

p5 <- ggplot(diamonds, aes(x = price)) +
geom_histogram(fill = "pink", colour = "brown", size = .3) +
scale_y_continuous( name = "Number of diamonds" ) +
scale_x_continuous( name = "Price" ) +
facet_wrap(~cut) +
theme(
axis.title.x = element_text(
size = rel(1.2), lineheight = .9,
family = "Calibri", face = "bold", colour = "black"
),
axis.title.y = element_text(
size = rel(1.2), lineheight = .9,
family = "Calibri", face = "bold", colour = "black"
),
plot.background = element_rect("yellow"))

p5
`````` Write for us
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