Hello -
Chip Barnaby wrote:
Dear all --
I want to compute weighted.mean() for grouped rows.
Data frame extract is just below. For each Key, I want the mean of IAC
weighted by Wt.
DP0[1:20,]
Key
IAC Wt
2 C3-PD030020050.PD030020050.3.12.3.0 0.765 0.8590000
3 C3-PD030020050.PD030020050.3.12.3.0 0.764 0.8449651
4 C3-PD030020050.PD030020050.3.12.3.0 0.760 0.8024975
5 C3-PD030020050.PD030020050.3.12.3.0 0.753 0.7326575
6 C3-PD030020050.PD030020050.3.12.3.0 0.743 0.6381150
7 C3-PD030020050.PD030020050.3.12.3.0 0.730 0.5187296
8 C3-PD030020050.PD030020050.3.12.3.0 0.714 0.3780000
65 C3-PD000000000.PD000000000.3.12.3.0 0.770 0.8590000
66 C3-PD000000000.PD000000000.3.12.3.0 0.770 0.8449651
67 C3-PD000000000.PD000000000.3.12.3.0 0.771 0.8024975
68 C3-PD000000000.PD000000000.3.12.3.0 0.772 0.7326575
69 C3-PD000000000.PD000000000.3.12.3.0 0.774 0.6381150
70 C3-PD000000000.PD000000000.3.12.3.0 0.777 0.5187296
71 C3-PD000000000.PD000000000.3.12.3.0 0.780 0.3780000
128 C3-PD000020000.PD000020000.3.12.3.0 0.685 0.8590000
129 C3-PD000020000.PD000020000.3.12.3.0 0.685 0.8449651
130 C3-PD000020000.PD000020000.3.12.3.0 0.684 0.8024975
131 C3-PD000020000.PD000020000.3.12.3.0 0.682 0.7326575
132 C3-PD000020000.PD000020000.3.12.3.0 0.679 0.6381150
133 C3-PD000020000.PD000020000.3.12.3.0 0.675 0.5187296
mean -- works OK
> MN = by( DP0$IAC, DP0$Key, mean)
weighted.mean -- no go due to length of Wt
> WMN = by( DP0$IAC, DP0$Key, weighted.mean, DP0$Wt)
Error in FUN(data[x, ], ...) : 'x' and 'w' must have the same length
Just a little confusion with how 'by' works I think, try
test <- data.frame(key = rep(c("A", "B"), each = 100),
iac = rnorm(200, 10),
wt = runif(200))
test
by(test, test$key, function(x) weighted.mean(x$iac, x$wt))
So I tried tapply() -- same result
> WMN = tapply( DP0, DP0$Key, function(x) weighted.mean( x$IAC, x$Wt))
Error in tapply(DP0, DP0$Key, function(x) weighted.mean(x$IAC, x$Wt)) :
arguments must have same length
How does one pass grouped arguments to processing functions such as
weighted.mean() ?
TIA,
Chip Barnaby
---------------------------------------------------------
Chip Barnaby [EMAIL PROTECTED]
Vice President of Research
Wrightsoft Corp. 781-862-8719 x118 voice
131 Hartwell Ave 781-861-2058 fax
Lexington, MA 02421 www.wrightsoft.com
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
