# [R] hist and truehist

Gregor GORJANC gregor.gorjanc at bfro.uni-lj.si
Fri Nov 26 17:21:45 CET 2004

Hello!

Up to now I have been using hist() to display the distributions.
Howevere, I noteiced strange numbers on y (vertical) axis, if I used
probability = T or freq = F option. I thought it is a bug and launched
the R-bug system and found some posts on that matter. Brian Ripley
responded to one, that one should look at truehist() for that. Ok I can
use truehist() if I want to see the ratios or probabilities, but what is
then the "density or probability" in hist()?

For example:

# some data
mydata <- c(1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,3,4,5)

# histogram with frequencies
hist(mydata)

# histogram with ratios or probabilities
hist(mydata, freq = F) # what are that values on vertical axis

# lets take a look at values behind
x <-hist(mydata, freq = F, plot = F); x

\$breaks
[1] 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

\$counts
[1] 22  1  0  1  0  1  0  1

\$intensities
[1] 1.69230735 0.07692308 0.00000000 0.07692308 0.00000000 0.07692308
0.00000000
[8] 0.07692308

\$density
[1] 1.69230735 0.07692308 0.00000000 0.07692308 0.00000000 0.07692308
0.00000000
[8] 0.07692308

\$mids
[1] 1.25 1.75 2.25 2.75 3.25 3.75 4.25 4.75

\$xname
[1] "mydata"

\$equidist
[1] TRUE

attr(,"class")
[1] "histogram"

# HOW are this intensities and density values calculated? What they
actually represent?

# MASS packages
library(MASS)

# again histogram with prob = T by default
truehist(mydata) # looks OK

--
Lep pozdrav / With regards / Con respeto,
Gregor GORJANC

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