I'm having trouble figuring out how to format Date variables when used
as axis labels in graphs.
The particular case here is an attempt to re-create Nightingale's
coxcomb graph with ggplot2,
where I'd like the months to be labeled as "Mar 1885", "Apr
1885", using
a date format
of "%b %Y" applied to label the dates, or really anything other than
"1885-03-01".
I know the solution has to do with formatting the dates, while
preserving their
status as an ordered factor, but I don't know how to do that.
Here's a subset of the data:
Night1 <-
structure(list(Date = structure(c(-42278, -42248, -42217, -42187,
-42156, -42125, -42095, -42064, -42034, -42003, -41972, -42278,
-42248, -42217, -42187, -42156, -42125, -42095, -42064, -42034,
-42003, -41972, -42278, -42248, -42217, -42187, -42156, -42125,
-42095, -42064, -42034, -42003, -41972), class = "Date"), Cause =
c("Disease",
"Disease", "Disease", "Disease",
"Disease", "Disease", "Disease",
"Disease", "Disease", "Disease",
"Disease", "Wounds", "Wounds",
"Wounds", "Wounds", "Wounds", "Wounds",
"Wounds", "Wounds", "Wounds",
"Wounds", "Wounds", "Other", "Other",
"Other", "Other", "Other",
"Other", "Other", "Other", "Other",
"Other", "Other"), Deaths = c(1.4,
6.2, 4.7, 150, 328.5, 312.2, 197, 340.6, 631.5, 1022.8, 822.8,
0, 0, 0, 0, 0.4, 32.1, 51.7, 115.8, 41.7, 30.7, 16.3, 7, 4.6,
2.5, 9.6, 11.9, 27.7, 50.1, 42.8, 48, 120, 140.1), Regime = structure(c(1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L
), .Label = c("Before", "After"), class =
c("ordered", "factor"
))), .Names = c("Date", "Cause", "Deaths",
"Regime"), row.names = c(1L,
2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 25L, 26L, 27L, 28L,
29L, 30L, 31L, 32L, 33L, 34L, 35L, 49L, 50L, 51L, 52L, 53L, 54L,
55L, 56L, 57L, 58L, 59L), class = "data.frame")
> str(Night1)
'data.frame': 33 obs. of 4 variables:
$ Date :Class 'Date' num [1:33] -42278 -42248 -42217 -42187 -42156 ...
$ Cause : chr "Disease" "Disease" "Disease"
"Disease" ...
$ Deaths: num 1.4 6.2 4.7 150 328.5 ...
$ Regime: Ord.factor w/ 2 levels "Before"<"After": 1 1 1
1 1 1 1 1 1 1 ...
>
Here are a few things I've tried, some of which give errors and others
of which
simply give the wrong graph
library(ggplot2)
cxc1 <- ggplot(Night1, aes(x = factor(Date), y=Deaths, fill = Cause)) +
# do it as a stacked bar chart first
geom_bar(width = 1, position="identity", color="black") +
# set scale so area ~ Deaths
scale_y_sqrt()
# A coxcomb plot = bar chart + polar coordinates
cxc1 + coord_polar(start=3*pi/2) + opts(title="Causes of Mortality in
the Army in the East") + xlab("")
# why doesn't this work?
cxc1 <- cxc1 + scale_x_date(format="%b %Y",
major="months")
cxc1
stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust
this.
OK, I tried formatting Date first, in different ways. Each time, I get
a graphical result, but I
don't know how to use format() for dates to make the result ordered as
normal dates, rather
than as character strings.
Night1$dt1 <- format(Night1$Date, "%b %Y")
cxc1 <- ggplot(Night1, aes(x = factor(dt1), y=Deaths, fill = Cause)) +
geom_bar(width = 1, position="identity", color="black") +
scale_y_sqrt()
cxc1 + coord_polar(start=3*pi/2) + opts(title="Causes of Mortality in
the Army in the East") + xlab("")
-Michael
--
Michael Friendly Email: friendly at yorku.ca
Professor, Psychology Dept.
York University Voice: 416 736-5115 x66249 Fax: 416 736-5814
4700 Keele Street http://www.math.yorku.ca/SCS/friendly.html
Toronto, ONT M3J 1P3 CANADA
Hi Michael,> I'm having trouble figuring out how to format Date variables when used as > axis labels in graphs. > The particular case here is an attempt to re-create Nightingale's coxcomb > graph with ggplot2, > where I'd like the months to be labeled as "Mar 1885", "Apr 1885", using a > date format > of "%b %Y" applied to label the dates, or really anything other than > "1885-03-01". I know the solution has to do with formatting the dates, while > preserving their > status as an ordered factor, but I don't know how to do that.Dates are, by their very nature, ordered so you don't need to keep them as an ordered factor. If you don't do that you'll find that the scale_date formatting options will work. Hadley -- http://had.co.nz/
hadley wickham wrote:> Hi Michael, > >> > I'm having trouble figuring out how to format Date variables when used as >> > axis labels in graphs. >> > The particular case here is an attempt to re-create Nightingale's coxcomb >> > graph with ggplot2, >> > where I'd like the months to be labeled as "Mar 1885", "Apr 1885", using a >> > date format >> > of "%b %Y" applied to label the dates, or really anything other than >> > "1885-03-01". I know the solution has to do with formatting the dates, while >> > preserving their >> > status as an ordered factor, but I don't know how to do that. > > Dates are, by their very nature, ordered so you don't need to keep > them as an ordered factor. If you don't do that you'll find that the > scale_date formatting options will work.I would have thought so, but I get an error unless I use aes(x=factor(Date)...) or aes(x=ordered(Date)...) in the original call to ggplot: > cxc1 <- ggplot(Night1, aes(x = Date, y=Deaths, fill = Cause)) + + # do it as a stacked bar chart first + geom_bar(width = 1, position="identity", color="black") + + # set scale so area ~ Deaths + scale_y_sqrt() > # A coxcomb plot = bar chart + polar coordinates > cxc1 + coord_polar(start=3*pi/2) + opts(title="Causes of Mortality in the Army in the East") + xlab("") stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this. Error in pmin(y, 0) : object 'y' not found I apologize for including attachments, but I can't get to a server where I can place the results as links. If I use aes(x=factor(Date)...), I get an appropriate graph, except that the dates appear as "1885-03-01". [See attached: night1-factor.png] With aes(x=ordered(Date)...), the same code gives only a bar chart [night1-ordered.png] If I format the date first, I get a result where the dates are ordered alphabetically [night1-formatted.png] Night1$dt1 <- format(Night1$Date, "%b %Y") cxc1 <- ggplot(Night1, aes(x = factor(dt1), y=Deaths, fill = Cause)) + geom_bar(width = 1, position="identity", color="black") + scale_y_sqrt() cxc1 + coord_polar(start=3*pi/2) + opts(title="Causes of Mortality in the Army in the East") + xlab("") For completeness, here is the data I was using: Night1 <- structure(list(Date = structure(c(-42278, -42248, -42217, -42187, -42156, -42125, -42095, -42064, -42034, -42003, -41972, -42278, -42248, -42217, -42187, -42156, -42125, -42095, -42064, -42034, -42003, -41972, -42278, -42248, -42217, -42187, -42156, -42125, -42095, -42064, -42034, -42003, -41972), class = "Date"), Cause = c("Disease", "Disease", "Disease", "Disease", "Disease", "Disease", "Disease", "Disease", "Disease", "Disease", "Disease", "Wounds", "Wounds", "Wounds", "Wounds", "Wounds", "Wounds", "Wounds", "Wounds", "Wounds", "Wounds", "Wounds", "Other", "Other", "Other", "Other", "Other", "Other", "Other", "Other", "Other", "Other", "Other"), Deaths = c(1.4, 6.2, 4.7, 150, 328.5, 312.2, 197, 340.6, 631.5, 1022.8, 822.8, 0, 0, 0, 0, 0.4, 32.1, 51.7, 115.8, 41.7, 30.7, 16.3, 7, 4.6, 2.5, 9.6, 11.9, 27.7, 50.1, 42.8, 48, 120, 140.1), Regime = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L ), .Label = c("Before", "After"), class = c("ordered", "factor" ))), .Names = c("Date", "Cause", "Deaths", "Regime"), row.names = c(1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 25L, 26L, 27L, 28L, 29L, 30L, 31L, 32L, 33L, 34L, 35L, 49L, 50L, 51L, 52L, 53L, 54L, 55L, 56L, 57L, 58L, 59L), class = "data.frame") -Michael -------------- next part -------------- A non-text attachment was scrubbed... Name: night1-factor.png Type: image/png Size: 39591 bytes Desc: not available URL: <https://stat.ethz.ch/pipermail/r-help/attachments/20091121/76b0c976/attachment-0006.png> -------------- next part -------------- A non-text attachment was scrubbed... Name: night1-ordered.png Type: image/png Size: 27564 bytes Desc: not available URL: <https://stat.ethz.ch/pipermail/r-help/attachments/20091121/76b0c976/attachment-0007.png> -------------- next part -------------- A non-text attachment was scrubbed... Name: night1-formatted.png Type: image/png Size: 39742 bytes Desc: not available URL: <https://stat.ethz.ch/pipermail/r-help/attachments/20091121/76b0c976/attachment-0008.png>