# [R] tapply grand mean

Chuck Cleland ccleland at optonline.net
Wed Aug 8 14:32:23 CEST 2007

```Lauri Nikkinen wrote:
> Hi R-users,
>
> I have a data.frame like this (modificated from
> https://stat.ethz.ch/pipermail/r-help/2007-August/138124.html).
>
> y1 <- rnorm(20) + 6.8
> y2 <- rnorm(20) + (1:20*1.7 + 1)
> y3 <- rnorm(20) + (1:20*6.7 + 3.7)
> y <- c(y1,y2,y3)
> x <- rep(1:5,12)
> f <- gl(3,20, labels=paste("lev", 1:3, sep=""))
> d <- data.frame(x=x,y=y, f=f)
>
> and this is how I can calculate mean of these levels.
>
> tapply(d\$y, list(d\$x, d\$f), mean)
>
> But how can I calculate the mean of d\$x 1 and 2 and the grand mean of d\$x 1,
> 2, 3, 4, 5 (within d\$f) into a table?

You might like the tables produced by summary.formula() in the Hmisc
package:

library(Hmisc)

summary(y ~ x + f, data = d, fun=mean, method="cross", overall=TRUE)

UseMethod by x, f

+-+
|N|
|y|
+-+
+---+---------+---------+---------+---------+
| x |   lev1  |   lev2  |   lev3  |   ALL   |
+---+---------+---------+---------+---------+
|1  | 4       | 4       | 4       |12       |
|   | 6.452326|15.861256|61.393455|27.902346|
+---+---------+---------+---------+---------+
|2  | 4       | 4       | 4       |12       |
|   | 7.403041|17.296270|68.208299|30.969203|
+---+---------+---------+---------+---------+
|3  | 4       | 4       | 4       |12       |
|   | 6.117648|17.976864|73.479837|32.524783|
+---+---------+---------+---------+---------+
|4  | 4       | 4       | 4       |12       |
|   | 7.831390|19.696998|80.323382|35.950590|
+---+---------+---------+---------+---------+
|5  | 4       | 4       | 4       |12       |
|   | 6.746213|21.101952|87.430087|38.426084|
+---+---------+---------+---------+---------+
|ALL|20       |20       |20       |60       |
|   | 6.910124|18.386668|74.167012|33.154601|
+---+---------+---------+---------+---------+

summary(y ~ I(x %in% c(1,2)) + f, data = d, fun=mean, method="cross",
overall=TRUE)

UseMethod by I(x %in% c(1, 2)), f

+-+
|N|
|y|
+-+
+-----------------+---------+---------+---------+---------+
|I(x %in% c(1, 2))|   lev1  |   lev2  |   lev3  |   ALL   |
+-----------------+---------+---------+---------+---------+
|      FALSE      |12       |12       |12       |36       |
|                 | 6.898417|19.591938|80.411102|35.633819|
+-----------------+---------+---------+---------+---------+
|      TRUE       | 8       | 8       | 8       |24       |
|                 | 6.927684|16.578763|64.800877|29.435774|
+-----------------+---------+---------+---------+---------+
|      ALL        |20       |20       |20       |60       |
|                 | 6.910124|18.386668|74.167012|33.154601|
+-----------------+---------+---------+---------+---------+

> Regards,
> Lauri
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> and provide commented, minimal, self-contained, reproducible code.

--
Chuck Cleland, Ph.D.
NDRI, Inc.
71 West 23rd Street, 8th floor
New York, NY 10010
tel: (212) 845-4495 (Tu, Th)
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```