[R] Strange graphical pattern when using hist() function

[Kevin E. Thorpe]

On 04/23/2013 01:40 PM, Humberto Mohr wrote:
> Running the following lines I got a strange plot from hist function:
>
> x<-0:30
> hist(x,breaks=31)
>
> As you can see, the 0 value appears two times in the plot.
> The Y axis only presents 1 as the highest value when:
>
> hist(x,breaks=62)
>
> Nevertheless, it seems to have two bars between 0 and 1.
>
> Could someone please explain to me why it is happening?
>
> Many thanks in advance!
>

I think if you do print(hist(x,breaks=31)) you will see it.

The "zero" bin has the values for zero and one.  There are 30 bins, not 
31, as I think you are expecting.

Take a look at the ?hist to understand how the bins are constructed.

-- 
Kevin E. Thorpe
Head of Biostatistics,  Applied Health Research Centre (AHRC)
Li Ka Shing Knowledge Institute of St. Michael's
Assistant Professor, Dalla Lana School of Public Health
University of Toronto
email: kevin.thorpe at utoronto.ca  Tel: 416.864.5776  Fax: 416.864.3016