[R] How is the relation between Frequency and Counts in hist/density defined?

[jim holtman]

try this -- it scales to the maximum value:

set.seed(242)
z = rnorm(30)
hist_z <- hist(z)
hist_z$counts / hist_z$density # the relation is 15
# why is this 15 ??
# So I can now do:
hist(z)
# change in this statement - scale to the max
y <- density(z)$y  * max(hist_z$counts) / max(density(z)$y)
#is what I hope to find without using hist, and only using density
x <- density(z)$x
lines(x = x, y = y, col = "blue", lwd = 5)



On Mon, May 23, 2011 at 10:56 AM,  <Richard.Cotton at hsl.gov.uk> wrote:
>
>   > In order to do this I can use the relation between count and density, but
>   I
>   > would like to know if there is a way for me to predict it upfront.
>   In the code for hist.default, you'll see the line
>   dens <- counts/(n * diff(breaks))
>   > Here is an example:
>   >
>   > set.seed(242)
>   > z = rnorm(30)
>   > hist_z <- hist(z)
>   > hist_z$counts / hist_z$density # the relation is 15
>   In your example, n is 30, and the breaks are evenly spaced every 0.5.
>   Regards,
>   Richie.
>   Mathematical Sciences Unit
>   [1]HSL
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-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?