[R] shading between two smoothed curves
Graves, Gregory
ggraves at sfwmd.gov
Fri Aug 14 14:16:09 CEST 2009
I will attempt to distill my problem down to a simpler one, the solution of which will hopefully lead me to the nirvana of complete understanding, i.e., inserting a polygon beneath an irregular line terminated by the x axis.
I 'know' that polygon will work -provided- I knew the xy coordinates of the line(s) beneath which I desire to create the polygon. Unfortunately, I don't know how to get at that info.
Below is an example of a irregular line for which the xy coordinates are not known (i.e., at least not by me). I assume my problem boils down to finding out how to extract the xy from that line.
attach(cars)
plot(dist ~ speed)
scatter.smooth(speed, dist,family = "gaussian",span = .2)
Gregory A. Graves
Lead Scientist
Everglades REstoration COoordination and VERification (RECOVER)
Watershed Division
South Florida Water Management District
Phones: DESK: 561 / 682 - 2429
CELL: 561 / 719 - 8157
From: Debabrata Midya [mailto:Debabrata.Midya at commerce.nsw.gov.au]
Sent: Thursday, August 13, 2009 6:36 PM
To: Graves, Gregory
Cc: r-help at r-project.org
Subject: Re: [R] shading between two smoothed curves
Hi Gregory,
> I can plot out two nice curves using the following code, but I can't
figure out how to shade in the area lying between the two curves.
Use polygon.
> ?polygon
>>> "Graves, Gregory" <ggraves at sfwmd.gov> 14/08/2009 4:17 am >>>
I have a set of 52 weekly values, one is the desired high lake stage for
a week, and the other is the desired low lake stage for each week. It
looks like this:
week
High
Low
1
16
14.5
2
16
14.5
3
15.95
14.45
4
15.84
14.34
5
15.73
14.23
6
15.61
14.11
7
15.5
14
8
15.38
13.88
9
15.25
13.75
10
15.13
13.63
....
52
15
13.5
I can plot out two nice curves using the following code, but I can't
figure out how to shade in the area lying between the two curves. I
also can't figure out how to adjust the line weight as lwd doesn't seem
to affect scatter.smooth. Thanks in advance.
l=11 #lower ylim
h=17 #upper ylim
par(new=F)
good <- complete.cases(week, high) #get rid of the NA error and only
using non-missing pairs
par(new=T)
scatter.smooth(week[good], high[good],family = "gaussian",span = .2,
ylim=c(l,h), type='n', lwd=2, color="blue", ylab="", xlab="")
good <- complete.cases(week, low)
par(new=T)
scatter.smooth(week[good], low[good],family = "gaussian",span = .2,
ylim=c(l,h), type='n', lwd=2, color="red", ylab="Stage, feet",
xlab="Week of Year") #loess, lower span makes more irregular
par(new=F)
Gregory A. Graves
Lead Scientist
Everglades REstoration COoordination and VERification (RECOVER)
Watershed Division
South Florida Water Management District
Phones: DESK: 561 / 682 - 2429
CELL: 561 / 719 - 8157
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