Fitting a density curve to a histogram in R

Question

Is there a function in R that fits a curve to a histogram   Let s say you had the following histogram  hist c rep 65  times 5   rep 25  times 5   rep 35  times 10   rep 45  times 4      It looks normal  but it s skewed  I want to fit a normal curve that is skewed to wrap around this histogram   This question is rather basic  but I can t seem to find the answer for R on the internet

User · Answer

Such thing is easy with ggplot2  library ggplot2  dataset  lt - data frame X   c rep 65  times 5   rep 25  times 5                                rep 35  times 10   rep 45  times 4    ggplot dataset  aes x   X        geom histogram aes y     density          geom density     or to mimic the result from Dirk s solution  ggplot dataset  aes x   X        geom histogram aes y     density     binwidth   5       geom density

User · Answer

I had the same problem but Dirk s solution didn t seem to work   I was getting this warning messege every time   prob  is not a graphical parameter   I read through  hist and found about freq  a logical vector set TRUE by default   the code that worked for me is  hist x freq FALSE  lines density x  na rm TRUE

User · Answer

If I understand your question correctly  then you probably want a density estimate along with the histogram   X  lt - c rep 65  times 5   rep 25  times 5   rep 35  times 10   rep 45  times 4   hist X  prob TRUE               prob TRUE for probabilities not counts lines density X                 add a density estimate with defaults lines density X  adjust 2   lty  dotted       add another  smoother  density   Edit a long while later   Here is a slightly more dressed-up version   X  lt - c rep 65  times 5   rep 25  times 5   rep 35  times 10   rep 45  times 4   hist X  prob TRUE  col  grey    prob TRUE for probabilities not counts lines density X   col  blue   lwd 2    add a density estimate with defaults lines density X  adjust 2   lty  dotted   col  darkgreen   lwd 2     along with the graph it produces

User · Answer

Dirk has explained how to plot the density function over the histogram  But sometimes you might want to go with the stronger assumption of a skewed normal distribution and plot that instead of density  You can estimate the parameters of the distribution and plot it using the sn package    gt  sn mle y c rep 65  times 5   rep 25  times 5   rep 35  times 10   rep 45  times 4     call sn mle y   c rep 65  times   5   rep 25  times   5   rep 35       times   10   rep 45  times   4      cp     mean     s d  skewness  41 46228 12 47892  0 99527      This probably works better on data that is more skew-normal

User · Answer

Here s the way I do it   foo  lt - rnorm 100  mean 1  sd 2  hist foo  prob TRUE  curve dnorm x  mean mean foo   sd sd foo    add TRUE    A bonus exercise is to do this with ggplot2 package

[r] Fitting a density curve to a histogram in R

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