Message-ID: <AANLkTinKF7iQ_+zUtpdV8M37pJ-9t7p+8MJRR+GPc9Ge@mail.gmail.com>
Date: 2010-09-08T20:07:13Z
From: Joshua Wiley
Subject: Correlation question
In-Reply-To: <Pine.LNX.4.63.1009081511250.12993@magret.iro.umontreal.ca>
Hi,
Does your data have missing values? I am not sure it would change
anything, but perhaps try adding:
cor(test2, method = "spearman", use = "pairwise.complete.obs")
or something of the like. I am not sure what R does by default. My
reasoning stems from this particular passage in the documentation:
If ?use? is ?"everything"?, ?NA?s will propagate conceptually,
i.e., a resulting value will be ?NA? whenever one of its
contributing observations is ?NA?.
I do not think the names should make a difference (unless you're
talking about human error).
Best regards,
Josh
On Wed, Sep 8, 2010 at 12:35 PM, Stephane Vaucher
<vauchers at iro.umontreal.ca> wrote:
> Hi everyone,
>
> I'm observing what I believe is weird behaviour when attempting to do
> something very simple. I want a correlation matrix, but my matrix seems to
> contain correlation values that are not found when executed on pairs:
>
>> test2$P2
>
> ?[1] 2 2 4 4 1 3 2 4 3 3 2 3 4 1 2 2 4 3 4 1 2 3 2 1 3
>>
>> test2$HP_tot
>
> ?[1] ?10 ?10 ?10 ?10 ?10 ?10 ?10 ?10 136 136 136 136 136 136 136 136 136 136
> ?15
> [20] ?15 ?15 ?15 ?15 ?15 ?15 c=cor(test2$P3,test2$HP_tot,method='spearman')
>>
>> c
>
> [1] -0.2182876
>>
>> c=cor(test2,method='spearman')
>
> Warning message:
> In cor(test2, method = "spearman") : the standard deviation is zero
>>
>> write(c,file='out.csv')
>
> from my spreadsheet
> -0.25028783918741
>
> Most cells are correct, but not that one.
>
> If this is expected behaviour, I apologise for bothering you, I read the
> documentation, but I do not know if the calculation of matrices and pairs is
> done using the same function (eg, with respect to equal value observations).
>
> If this is not a desired behaviour, I noticed that it only occurs with a
> relatively large matrix (I couldn't reproduce on a simple 2 column data
> set). There might be a naming error.
>
>> names(test2)
>
> ?[1] "ID" ? ? ? ? ? ? ? ? ? "NOMBRE" ? ? ? ? ? ? ? "MAIL"
> ?[4] "Age" ? ? ? ? ? ? ? ? ?"SEXO" ? ? ? ? ? ? ? ? "Studies"
> ?[7] "Hours_Internet" ? ? ? "Vision.Disabilities" ?"Other.disabilities"
> [10] "Technology_Knowledge" "Start_Time" ? ? ? ? ? "End_Time"
> [13] "Duration" ? ? ? ? ? ? "P1" ? ? ? ? ? ? ? ? ? "P1Book"
> [16] "P1DVD" ? ? ? ? ? ? ? ?"P2" ? ? ? ? ? ? ? ? ? "P3"
> [19] "P4" ? ? ? ? ? ? ? ? ? "P5" ? ? ? ? ? ? ? ? ? "P6"
> [22] "P8" ? ? ? ? ? ? ? ? ? "P9" ? ? ? ? ? ? ? ? ? "P10"
> [25] "P11" ? ? ? ? ? ? ? ? ?"P12" ? ? ? ? ? ? ? ? ?"P7"
> [28] "SITE" ? ? ? ? ? ? ? ? "Errors" ? ? ? ? ? ? ? "warnings"
> [31] "Manual" ? ? ? ? ? ? ? "Total" ? ? ? ? ? ? ? ?"H_tot"
> [34] "HP1.1" ? ? ? ? ? ? ? ?"HP1.2" ? ? ? ? ? ? ? ?"HP1.3"
> [37] "HP1.4" ? ? ? ? ? ? ? ?"HP_tot" ? ? ? ? ? ? ? "HO1.1"
> [40] "HO1.2" ? ? ? ? ? ? ? ?"HO1.3" ? ? ? ? ? ? ? ?"HO1.4"
> [43] "HO_tot" ? ? ? ? ? ? ? "HU1.1" ? ? ? ? ? ? ? ?"HU1.2"
> [46] "HU1.3" ? ? ? ? ? ? ? ?"HU_tot" ? ? ? ? ? ? ? "HR"
> [49] "L_tot" ? ? ? ? ? ? ? ?"LP1.1" ? ? ? ? ? ? ? ?"LP1.2"
> [52] "LP1.3" ? ? ? ? ? ? ? ?"LP1.4" ? ? ? ? ? ? ? ?"LP_tot"
> [55] "LO1.1" ? ? ? ? ? ? ? ?"LO1.2" ? ? ? ? ? ? ? ?"LO1.3"
> [58] "LO1.4" ? ? ? ? ? ? ? ?"LO_tot" ? ? ? ? ? ? ? "LU1.1"
> [61] "LU1.2" ? ? ? ? ? ? ? ?"LU1.3" ? ? ? ? ? ? ? ?"LU_tot"
> [64] "LR_tot" ? ? ? ? ? ? ? "SP_tot" ? ? ? ? ? ? ? "SP1.1"
> [67] "SP1.2" ? ? ? ? ? ? ? ?"SP1.3" ? ? ? ? ? ? ? ?"SP1.4"
> [70] "SP_tot.1" ? ? ? ? ? ? "SO1.1" ? ? ? ? ? ? ? ?"SO1.2"
> [73] "SO1.3" ? ? ? ? ? ? ? ?"SO1.4" ? ? ? ? ? ? ? ?"SO_tot"
> [76] "SU1.1" ? ? ? ? ? ? ? ?"SU1.2" ? ? ? ? ? ? ? ?"SU1.3"
> [79] "SU_tot" ? ? ? ? ? ? ? "SR"
>
> Thank you in advance,
> Stephane Vaucher
>
> ______________________________________________
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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.
>
--
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/