Overlaying histograms with ggplot2 in R

Question

I am new to R and am trying to plot 3 histograms onto the same graph  Everything worked fine  but my problem is that you don t see where 2 histograms overlap - they look rather cut off  When I make density plots  it looks perfect  each curve is surrounded by a black frame line  and colours look different where curves overlap  Can someone tell me if something similar can be achieved with the histograms in the 1st picture  This is the code I m using  lowf0  lt -read csv        mediumf0  lt -read csv        highf0  lt -read csv       lowf0 utt lt - low f0  mediumf0 utt lt - medium f0  highf0 utt lt - high f0  histogram lt -rbind lowf0 mediumf0 highf0  ggplot histogram  aes f0  fill   utt     geom histogram alpha   0 2

User · Answer

Using  joran s sample data   ggplot dat  aes x xx  fill yy     geom histogram alpha 0 2  position  identity     note that the default position of geom histogram is  stack    see  position adjustment  of this page    docs ggplot2 org current geom histogram html

User · Answer

Your current code   ggplot histogram  aes f0  fill   utt     geom histogram alpha   0 2    is telling ggplot to construct one histogram using all the values in f0 and then color the bars of this single histogram according to the variable utt   What you want instead is to create three separate histograms  with alpha blending so that they are visible through each other  So you probably want to use three separate calls to geom histogram  where each one gets it s own data frame and fill   ggplot histogram  aes f0          geom histogram data   lowf0  fill    red   alpha   0 2         geom histogram data   mediumf0  fill    blue   alpha   0 2        geom histogram data   highf0  fill    green   alpha   0 2      Here s a concrete example with some output   dat  lt - data frame xx   c runif 100 20 50  runif 100 40 80  runif 100 0 30   yy   rep letters 1 3  each   100    ggplot dat aes x xx          geom histogram data subset dat yy     a   fill    red   alpha   0 2        geom histogram data subset dat yy     b   fill    blue   alpha   0 2        geom histogram data subset dat yy     c   fill    green   alpha   0 2    which produces something like this     Edited to fix typos  you wanted fill  not colour

User · Answer

While only a few lines are required to plot multiple overlapping histograms in ggplot2  the results are t always satisfactory  There needs to be proper use of borders and coloring to ensure the eye can differentiate between histograms    The following functions balance border colors  opacities  and superimposed density plots to enable the viewer to differentiate among distributions    Single histogram   plot histogram  lt - function df  feature        plt  lt - ggplot df  aes x eval parse text feature           geom histogram aes y     density     alpha 0 7  fill   33AADE   color  black         geom density alpha 0 3  fill  red         geom vline aes xintercept mean eval parse text feature      color  black   linetype  dashed   size 1        labs x feature  y    Density       print plt      Multiple histogram   plot multi histogram  lt - function df  feature  label column        plt  lt - ggplot df  aes x eval parse text feature    fill eval parse text label column           geom histogram alpha 0 7  position  identity   aes y     density     color  black         geom density alpha 0 7        geom vline aes xintercept mean eval parse text feature      color  black   linetype  dashed   size 1        labs x feature  y    Density       plt   guides fill guide legend title label column       Usage   Simply pass your data frame into the above functions along with desired arguments   plot histogram iris   Sepal Width       plot multi histogram iris   Sepal Width    Species       The extra parameter in plot multi histogram is the name of the column containing the category labels   We can see this more dramatically by creating a dataframe with many different distribution means   a  lt -data frame n rnorm 1000  mean   1   category rep  A   1000   b  lt -data frame n rnorm 1000  mean   2   category rep  B   1000   c  lt -data frame n rnorm 1000  mean   3   category rep  C   1000   d  lt -data frame n rnorm 1000  mean   4   category rep  D   1000   e  lt -data frame n rnorm 1000  mean   5   category rep  E   1000   f  lt -data frame n rnorm 1000  mean   6   category rep  F   1000   many distros  lt - do call  rbind   list a b c d e f     Passing data frame in as before  and widening chart using options    options repr plot width   20  repr plot height   8  plot multi histogram many distros   n    category

[r] Overlaying histograms with ggplot2 in R

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