For the mean, there is a function called weighted.mean() and you can use it as a start for custom functions. An alternative is to expand your grouped data before applying your function, e.a. > x <- rep(wtc$MIDPOINT, wtc$FREQ) > c(Mean=mean(x), Var=var(x)) but it isn't appropriate for some parameters (it doesn't give interpolated median, etc)
At 04:01 14/11/02, you wrote:
Date: Wed, 13 Nov 2002 10:04:00 -0500
From: Matej Cepl <matej at ceplovi.cz>
Subject: [R] [Newbie] Is there any support for work with grouped frequencies?
Hi,
I have this table (BTW, published by FBI and representing age
distribution of the WTC tragedy victims):
"LABEL" "FREQ" "MIDPOINT"
"1" "Infant (under 1)" 0
"2" "1 to 4" 5
"3" "5 to 8" 1
"4" "9 to 12" 3
"5" "13 to 16" 0
"6" "17 to 19" 3
"7" "20 to 24" 117
"8" "25 to 29" 341
"9" "30 to 34" 503
"10" "35 to 39" 578
"11" "40 to 44" 510
"12" "45 to 49" 369
"13" "50 to 54" 272
"14" "55 to 59" 177
"15" "60 to 64" 79
"16" "65 to 69" 29
"17" "70 to 74" 15
"18" "75 and over" 11
"19" "Unknown" NA
Are there any tools to work with grouped frequencies (i.e.,
median, mean, chi-square test of normality of distribution) or do
I have to calculate them ``by hand''?
Thanks for any answer,
Matej
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