A heatmap() function in R is used to visualize data in the form of a heatmap. A heatmap is a graphical representation where values in a matrix are represented using colors. Higher values are typically shown using brighter or warmer colors (such as red), while lower values are represented using darker or cooler colors. It is commonly used to understand patterns, variations and intensity within data.
Syntax
heatmap(data)
Parameters:
- data: It represent matrix data, such as values of rows and columns
Create a Heatmap
In this example, number of rows and columns are specified to draw heatmap with a given function.
set.seed(110)
data <- matrix(rnorm(100, 0, 5), nrow = 10, ncol = 10)
colnames(data) <- paste0("col", 1:10)
rownames(data) <- paste0("row", 1:10)
heatmap(data)
Output:
Create Heatmap using colorRampPalette
In this example, heat map is drawn by using colorRampPalette to merge two different colors.
set.seed(110)
data <- matrix(rnorm(100, 0, 5), nrow = 10, ncol = 10)
colnames(data) <- paste0("col", 1:10)
rownames(data) <- paste0("row", 1:10)
my_colors <- colorRampPalette(c("cyan", "darkgreen"))
heatmap(data, col = my_colors(100))
Output:
Add Title and Axis Labels
In this example we give the title of the heatmap using the main argument and the xlab ,ylab arguments are used to label the x and y axes, respectively.
set.seed(110)
data <- matrix(rnorm(100, 0, 5), nrow = 10, ncol = 10)
colnames(data) <- paste0("col", 1:10)
rownames(data) <- paste0("row", 1:10)
my_colors <- colorRampPalette(c("cyan", "darkgreen"))
heatmap(data, col = my_colors(100), main = "Customized Heatmap",
xlab = "Columns", ylab = "Rows")
Output:
Adjust Margins Around the Plot
The margins argument controls the space around the plot. The first value (5) sets the bottom margin for column labels and the second value (10) sets the left margin for row labels.
set.seed(110)
data <- matrix(rnorm(100, 0, 5), nrow = 10, ncol = 10)
colnames(data) <- paste0("col", 1:10)
rownames(data) <- paste0("row", 1:10)
my_colors <- colorRampPalette(c("cyan", "darkgreen"))
heatmap(data, col = my_colors(100), main = "Customized Heatmap",
xlab = "Columns", ylab = "Rows", margins = c(5, 10))
Output:
Heatmap without Dendrogram
In this example we plot a heatmap without dendrograms by setting Colv = NA and Rowv = NA, which removes the hierarchical clustering and dendrogram from both rows and columns.
set.seed(110)
data <- matrix(rnorm(100, 0, 5), nrow = 10, ncol = 10)
colnames(data) <- paste0("col", 1:10)
rownames(data) <- paste0("row", 1:10)
my_colors <- colorRampPalette(c("cyan", "darkgreen"))
heatmap(data, col = my_colors(100), main = "Customized Heatmap",
xlab = "Columns", ylab = "Rows", margins = c(5, 10), Colv = NA, Rowv = NA)
Output:
You can download the complete source code from here.