[R] lattice histogram problem with integers values and nint

From: Richard and Barbara Males <rbmales_at_gmail.com>
Date: Thu, 15 May 2008 15:27:29 -0400

been puzzling over this for a day.

integer variable to use with histogram, 170,000 rows. Value is day of year. Hist works, lattice histogram with nint does not work (spurious spikes in display), lattice histogram using breaks=c(0:365) works fine. Spike values appear to be sum of two adjacent bins. Want to know if this is a familiar problem, and what the recommended work-around is. Also want to know how to get the bin count from the lattice histogram object, as I would with hist$count.

Thanks in advance.


I have a dataset of approximately 170,000 rows, with a DayOfYear field. I want a histogram of the number of rows in each day of the year. I set up breaks from 0:365, and use this with hist, and the lattice histogram, e.g.


If I use hist to display this, all values are under 600, everything is fine..

If I use lattice histogram on the full 365 days, either with nint=365, or breaks set from (0:366), I get 26 equally-spaced spurious peaks above 800 (that is, 26 days reported with bad values). A table command on this field shows me that the highest count of rows in a day is 553. When I do hist (not histogram), the plot looks fine. When I do plot(table(dataframe$DayOfYear), the plot looks fine. If I do a subset of the data to look only at days below 340, the plot looks fine. At days below 341, I get one of these spikes, at about 170 days, going up to about 900. At a subset of days below 342, I get two spikes, both over 900.

If I set breaks to 0:366, and add a small increment to my integer values, e.g.


All is well.under this approach.

I have attempted to search to see if this is a known problem, but don't find anything.

Also, I can get the count in each bin for hist as
> xx=hist(df2006NonRecVessels$DayOfYear,breaks=breaklist)
> xx$count # this gives me the counts

I am unclear how to get equivalent information on bin contents from the lattice-generated histogram object. It appears to be in panel.args, but I am unclear on the exact syntax.

Richard M. Males
Cincinnati, Ohio, USA

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