How do you specifically order ggplot2 x axis instead of alphabetical order

Question

I m trying to make a heatmap using ggplot2 using the geom tiles function here is my code below   p lt -ggplot data aes Treatment organisms   geom tile aes fill S      scale fill gradient low    black  high    red        scale x discrete expand   c 0  0        scale y discrete expand   c 0  0        theme legend position    right        axis ticks   element blank         axis text x   element text size   base size  angle   90  hjust   0  colour    black        axis text y   element text size   base size  hjust   1  colour    black       data is my data csv file my X axis is types of Treatment my Y axis is types of organisms    I m not too familiar with commands and programming and I m relatively new at this  I just want to be able to specify the order of the labels on the x axis  In this case  I m trying to specify the order of  Treatment   By default  it orders alphabetically  How do I override this keep the data in the same order as in my original csv file   I ve tried this command  scale x discrete limits c  Y   X   Z      where x  y and z are my treatment condition order  It however doesn t work very well  and give me missing heat boxes

User · Accepted Answer

It is a little difficult to answer your specific question without a full, reproducible example. However something like this should work:

#Turn your 'treatment' column into a character vector
data$Treatment <- as.character(data$Treatment)
#Then turn it back into a factor with the levels in the correct order
data$Treatment <- factor(data$Treatment, levels=unique(data$Treatment))

In this example, the order of the factor will be the same as in the data.csv file.

If you prefer a different order, you can order them by hand:

data$Treatment <- factor(data$Treatment, levels=c("Y", "X", "Z"))

However this is dangerous if you have a lot of levels: if you get any of them wrong, that will cause problems.

User · Answer

The accepted answer offers a solution which requires changing of the underlying data frame  This is not necessary  One can also simply factorise within the aes   call directly or create a vector for that instead  This is certainly not much different than user Drew Steen s answer  but with the important difference of not changing the original data frame  level order  lt - c  virginica    versicolor    setosa    this vector might be useful for other plots analyses  ggplot iris  aes x   factor Species  level   level order   y   Petal Width     geom col    or level order  lt - factor iris Species  level   c  virginica    versicolor    setosa     ggplot iris  aes x   level order  y   Petal Width     geom col    or directly in the aes   call without a pre-created vector  ggplot iris  aes x   factor Species  level   c  virginica    versicolor    setosa     y   Petal Width     geom col

[r] How do you specifically order ggplot2 x axis instead of alphabetical order?

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