Reshape Wide to Long
Let's use the Loblolly dataset from the datasets package. These data track the growth of some loblolly pine trees.> Loblolly[1:10,] height age Seed 1 4.51 3 301 15 10.89 5 301 29 28.72 10 301 43 41.74 15 301 57 52.70 20 301 71 60.92 25 301 2 4.55 3 303 16 10.92 5 303 30 29.07 10 303 44 42.83 15 303
First, we need to convert the data to wide form, so each age (i.e. 3, 5, 10, 15, 20, 25) will have its own variable.
wide <- reshape(Loblolly, v.names = "height", timevar = "age", idvar = "Seed", direction = "wide")
> wide[1:5,] Seed height.3 height.5 height.10 height.15 height.20 height.25 1 301 4.51 10.89 28.72 41.74 52.70 60.92 2 303 4.55 10.92 29.07 42.83 53.88 63.39 3 305 4.79 11.37 30.21 44.40 55.82 64.10 4 307 3.91 9.48 25.66 39.07 50.78 59.07 5 309 4.81 11.20 28.66 41.66 53.31 63.05
Create Variables
Then we want to create new columns showing how much each tree has grown between data points. For example, instead of knowing a tree's height at age 10, we want to know how much it's grown between age 5 and age 10, so that can be a bar in our graph.wide$h0.3 <- wide$height.3 wide$h3.5 <- wide$height.5 - wide$height.3 wide$h5.10 <- wide$height.10 - wide$height.5 wide$h10.15 <- wide$height.15 - wide$height.10 wide$h15.20 <- wide$height.20 - wide$height.15 wide$h20.25 <- wide$height.25 - wide$height.20
Plot Stacked Bar Chart
Finally, we want to plot all the new data points:library(RColorBrewer) sequential <- brewer.pal(6, "BuGn")
barplot(t(wide[,8:13]),
names.arg = wide$Seed, # x-axis labels
cex.names = 0.7, # makes x-axis labels small enough to show all
col = sequential, # colors
xlab = "Seed Source",
ylab = "Height, Feet",
xlim = c(0,20), # these two lines allow space for the legend
width = 1) # these two lines allow space for the legend
legend("bottomright",
legend = c("20-25", "15-20", "10-15", "5-10", "3-5", "0-3"), #in order from top to bottom
fill = sequential[6:1], # 6:1 reorders so legend order matches graph
title = "Years")
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| Stacked bar chart |
If you decide you'd rather have clustered bars instead of stacked bars, you can just add the option beside = TRUE to the barplot.
The full code is available in a gist.
The full code is available in a gist.
thanks for this - was very useful and I easily made my bar chart following this! (-:
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