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[BUGZILLA #4586] fivenum #1916

Closed MichaelChirico closed 4 years ago

MichaelChirico commented 4 years ago

From: r.huggins@<::CENSORED -- SEE ORIGINAL ON BUGZILLA::> Full_Name: Richard Huggins Version: 1.7.1 OS: windows 2000 Submission from: (NULL) (131.172.4.44)

x<-rnorm(100,2,1)
mean(x)

[1] 1.73299

summary(fivenum(x))

Min. 1st Qu. Median Mean 3rd Qu. Max. -0.3655 1.1070 1.7430 1.7320 2.3840 3.7910 

summary(x)

Min. 1st Qu. Median Mean 3rd Qu. Max. -0.3655 1.1070 1.7430 1.7330 2.3830 3.7910 

y<-log(abs(x))
summary(fivenum(y))

Min. 1st Qu. Median Mean 3rd Qu. Max. -3.5950 0.1020 0.5555 -0.1472 0.8688 1.3330 

mean(y)

[1] 0.2878568

summary(y)

Min. 1st Qu. Median Mean 3rd Qu. Max. -3.5950 0.1021 0.5555 0.2879 0.8683 1.3330

summary(fivenum(x)) gives the wrong mean

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MichaelChirico commented 4 years ago

From: Dirk Eddelbuettel <edd@<::CENSORED -- SEE ORIGINAL ON BUGZILLA::>> On Wed, Oct 15, 2003 at 01:20:04AM +0200, r.huggins@<::CENSORED -- SEE ORIGINAL ON BUGZILLA::> wrote:

Full_Name: Richard Huggins
Version: 1.7.1
OS: windows 2000
Submission from: (NULL) (131.172.4.44)

> x<-rnorm(100,2,1)
> mean(x)
[1] 1.73299
> summary(fivenum(x))
Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
-0.3655  1.1070  1.7430  1.7320  2.3840  3.7910 
> summary(x)
Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
-0.3655  1.1070  1.7430  1.7330  2.3830  3.7910 
> y<-log(abs(x))
> summary(fivenum(y))
Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
-3.5950  0.1020  0.5555 -0.1472  0.8688  1.3330 
> mean(y)
[1] 0.2878568
> summary(y)
Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
-3.5950  0.1021  0.5555  0.2879  0.8683  1.3330 

summary(fivenum(x)) gives the wrong mean

I think you may be misunderstanding what is happening -- fivenum() returns a simple vector of five numbers, which summary then summarises.

It so happens that for an (approx.) symmetrically distributed sample x as the one you drew from the N(2,1), mean(summary(x)) is still approx. mean(x) (and identical asymptocally). That no longer holds once you take logs(abs()). As so often, it helps to simply plot the data as you could with

boxplot(x,summary(x),fivenum(x),y,summary(y),fivenum(y),horizontal=TRUE)

Hth, Dirk

-- Those are my principles, and if you don't like them... well, I have others. -- Groucho Marx

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MichaelChirico commented 4 years ago

Audit (from Jitterbug): Wed Oct 15 02:14:47 2003 thomas moved from incoming to feature&FAQ

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