[R] Correlation question

Stephane Vaucher vauchers at iro.umontreal.ca
Thu Sep 9 04:23:54 CEST 2010


Hi everyone,

First of all, thanks for the quick responses. I appreciate the help.

Before answering questions, I wanted to mention that I tested this 
behaviour on 2.3.1 and 2.10.1 on a x86_64 linux arch, and on version 2.9.0 
on a 32 bit arch.

Now for the answers (batch version):

1/ I received another message stating that I mislabeled the data in my 
previous message. That was a retranscription error. I have included a 
sample of the data causing the problem

2/  On Wed, 8 Sep 2010, Joshua Wiley wrote:

> 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")

Tried, no difference. The specific pairwise comparisons do not contain 
missing values (other parts of my data, yes)


3/ From: Kjetil Halvorsen <kjetilbrinchmannhalvorsen at gmail.com>
> Do dput(test2) and copy&paste the output into the email messa<ge.

I had to clean up my data before sending it (had to remove names/emails).
Problems are visible with (spearman) correlations with P3 with H_tot and 
HP_tot. In my correlation matrix, these are both: -0.25028783918741 
instead of -0.2182876. Most other correlations are however accurate.

Here is the data:

> dput(exp)
> names(exp)
  [1] "P1"       "P2"       "P3"       "P4"       "P5"       "P6"
  [7] "P8"       "P9"       "P10"      "P11"      "P12"      "P7"
[13] "SITE"     "Errors"   "warnings" "Manual"   "Total"    "H_tot"
[19] "HP1.1"    "HP1.2"    "HP1.3"    "HP1.4"    "HP_tot"   "HO1.1"
[25] "HO1.2"    "HO1.3"    "HO1.4"    "HO_tot"   "HU1.1"    "HU1.2"
[31] "HU1.3"    "HU_tot"   "HR"       "L_tot"    "LP1.1"    "LP1.2"
[37] "LP1.3"    "LP1.4"    "LP_tot"   "LO1.1"    "LO1.2"    "LO1.3"
[43] "LO1.4"    "LO_tot"   "LU1.1"    "LU1.2"    "LU1.3"    "LU_tot"
[49] "LR_tot"   "SP_tot"   "SP1.1"    "SP1.2"    "SP1.3"    "SP1.4"
[55] "SP_tot.1" "SO1.1"    "SO1.2"    "SO1.3"    "SO1.4"    "SO_tot"
[61] "SU1.1"    "SU1.2"    "SU1.3"    "SU_tot"   "SR"
> dput(exp)
structure(list(P1 = c(2L, 1L, 3L, 3L, 2L, 3L, 2L, 3L, 3L, 2L,
2L, 2L, 4L, 1L, 3L, 2L, 3L, 2L, 3L, 2L, 2L, 2L, 2L, 1L, 2L),
     P2 = c(2L, 2L, 4L, 4L, 1L, 3L, 2L, 4L, 3L, 3L, 2L, 3L, 4L,
     1L, 2L, 2L, 4L, 3L, 4L, 1L, 2L, 3L, 2L, 1L, 3L), P3 = c(2L,
     2L, 2L, 4L, 2L, 3L, 2L, 1L, 3L, 2L, 2L, 2L, 3L, 1L, 2L, 1L,
     1L, 1L, 2L, 1L, 2L, 2L, 2L, 1L, 2L), P4 = c(1L, 3L, 3L, 4L,
     2L, 3L, 1L, 4L, 3L, 3L, 2L, 3L, 4L, 1L, 3L, 2L, 2L, 1L, 2L,
     1L, 1L, 2L, 1L, 1L, 2L), P5 = c(2L, 1L, 4L, 1L, 2L, 2L, 2L,
     3L, 3L, 2L, 2L, 3L, 4L, 1L, 2L, 2L, 3L, 3L, 3L, 2L, 2L, 2L,
     2L, 2L, 3L), P6 = c(2L, 2L, 4L, 1L, 2L, 2L, 2L, 2L, 3L, 2L,
     2L, 2L, 4L, 1L, 2L, 2L, 3L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 3L
     ), P8 = c(2L, 2L, 4L, 2L, 2L, 2L, 2L, 4L, 3L, 2L, 2L, 2L,
     4L, 1L, 3L, 2L, 3L, 2L, 3L, 2L, 2L, 2L, 2L, 2L, 2L), P9 = c(4L,
     0L, 4L, 0L, 0L, 2L, 3L, 0L, 0L, 4L, 0L, 4L, 3L, 2L, 4L, 0L,
     0L, 0L, 3L, 4L, 3L, 0L, 4L, 0L, 3L), P10 = c(3L, 3L, 2L,
     2L, 3L, 3L, 0L, 2L, 2L, 2L, 3L, 2L, 2L, 3L, 3L, 3L, 2L, 2L,
     2L, 3L, 3L, 2L, 3L, 3L, 3L), P11 = c(1L, 1L, 2L, 2L, 1L,
     1L, 0L, 2L, 2L, 1L, 1L, 1L, 2L, 1L, 1L, 1L, 1L, 2L, 1L, 1L,
     1L, 1L, 1L, 1L, 1L), P12 = c(9L, 10L, 6L, 5L, 9L, 8L, 0L,
     5L, 4L, 6L, 8L, 7L, 3L, 10L, 7L, 9L, 7L, 6L, 7L, 10L, 8L,
     7L, 8L, 9L, 7L), P7 = structure(c(1L, 9L, 7L, 8L, 1L, 3L,
     1L, 1L, 5L, 4L, 1L, 1L, 1L, 1L, 1L, 6L, 1L, 1L, 1L, 11L,
     10L, 1L, 2L, 1L, 1L), .Label = c(" ", " al inicio de la 
págia
conexión.",
     " al principio no sabes muy bien por donde empezar pero una vez 
aclarado es facil",
     " busqueda diferente alas conocidas", " CUando el título 
contiene dos puntos,no responde.",
     " Lass,suelen dar facilidades para 
buscar lo que se necesita.",
     " La verdad es que está un poco confusa la web y, si la persona 
que tiene que acceder a ella no es experta, creo que lo tiene difícil",
     " muy complicado, el poder encontrar los citados documentos, en la 
UNIVERSIDAD citada,",
     " Ninguna", " Que no hay pestañas q
de pelicula",
     " yo ninguna"), class = "factor"), SITE = c(5L, 5L, 5L,
     5L, 5L, 5L, 5L, 5L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L,
     1L, 1L, 1L, 1L, 1L, 1L, 1L), Errors = c(201L, 201L, 201L,
     201L, 201L, 201L, 201L, 201L, 369L, 369L, 369L, 369L, 369L,
     369L, 369L, 369L, 369L, 369L, 159L, 159L, 159L, 159L, 159L,
     159L, 159L), warnings = c(164L, 164L, 164L, 164L, 164L, 164L,
     164L, 164L, 447L, 447L, 447L, 447L, 447L, 447L, 447L, 447L,
     447L, 447L, 490L, 490L, 490L, 490L, 490L, 490L, 490L), Manual = c(44L,
     44L, 44L, 44L, 44L, 44L, 44L, 44L, 46L, 46L, 46L, 46L, 46L,
     46L, 46L, 46L, 46L, 46L, 45L, 45L, 45L, 45L, 45L, 45L, 45L
     ), Total = c(409L, 409L, 409L, 409L, 409L, 409L, 409L, 409L,
     862L, 862L, 862L, 862L, 862L, 862L, 862L, 862L, 862L, 862L,
     694L, 694L, 694L, 694L, 694L, 694L, 694L), H_tot = c(11L,
     11L, 11L, 11L, 11L, 11L, 11L, 11L, 140L, 140L, 140L, 140L,
     140L, 140L, 140L, 140L, 140L, 140L, 21L, 21L, 21L, 21L, 21L,
     21L, 21L), HP1.1 = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 1L,
     1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 4L, 4L, 4L, 4L, 4L, 4L,
     4L), HP1.2 = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L),
     HP1.3 = c(3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 94L, 94L, 94L,
     94L, 94L, 94L, 94L, 94L, 94L, 94L, 6L, 6L, 6L, 6L, 6L, 6L,
     6L), HP1.4 = c(7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 41L, 41L,
     41L, 41L, 41L, 41L, 41L, 41L, 41L, 41L, 5L, 5L, 5L, 5L, 5L,
     5L, 5L), HP_tot = c(10L, 10L, 10L, 10L, 10L, 10L, 10L, 10L,
     136L, 136L, 136L, 136L, 136L, 136L, 136L, 136L, 136L, 136L,
     15L, 15L, 15L, 15L, 15L, 15L, 15L), HO1.1 = c(0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     2L, 2L, 2L, 2L, 2L, 2L, 2L), HO1.2 = c(0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L), HO1.3 = c(0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L), HO1.4 = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L), HO_tot = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 2L, 2L, 2L, 2L, 2L, 2L, 2L),
     HU1.1 = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L), HU1.2 = c(0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), HU1.3 = c(0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
     1L, 1L, 1L, 1L, 1L, 1L, 1L), HU_tot = c(0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L,
     2L, 2L, 2L, 2L, 2L), HR = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
     3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 2L, 2L, 2L, 2L, 2L,
     2L, 2L), L_tot = c(26L, 26L, 26L, 26L, 26L, 26L, 26L, 26L,
     168L, 168L, 168L, 168L, 168L, 168L, 168L, 168L, 168L, 168L,
     95L, 95L, 95L, 95L, 95L, 95L, 95L), LP1.1 = c(2L, 2L, 2L,
     2L, 2L, 2L, 2L, 2L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L,
     16L, 16L, 16L, 16L, 16L, 16L, 16L), LP1.2 = c(0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L), LP1.3 = c(8L, 8L, 8L, 8L, 8L,
     8L, 8L, 8L, 110L, 110L, 110L, 110L, 110L, 110L, 110L, 110L,
     110L, 110L, 39L, 39L, 39L, 39L, 39L, 39L, 39L), LP1.4 = c(12L,
     12L, 12L, 12L, 12L, 12L, 12L, 12L, 41L, 41L, 41L, 41L, 41L,
     41L, 41L, 41L, 41L, 41L, 10L, 10L, 10L, 10L, 10L, 10L, 10L
     ), LP_tot = c(22L, 22L, 22L, 22L, 22L, 22L, 22L, 22L, 157L,
     157L, 157L, 157L, 157L, 157L, 157L, 157L, 157L, 157L, 65L,
     65L, 65L, 65L, 65L, 65L, 65L), LO1.1 = c(2L, 2L, 2L, 2L,
     2L, 2L, 2L, 2L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 14L,
     14L, 14L, 14L, 14L, 14L, 14L), LO1.2 = c(0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L), LO1.3 = c(0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L), LO1.4 = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 4L, 4L, 4L, 4L, 4L,
     4L, 4L), LO_tot = c(3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 18L, 18L, 18L, 18L, 18L,
     18L, 18L), LU1.1 = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L), LU1.2 = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 1L, 1L, 1L,
     1L, 1L, 1L, 1L, 1L, 1L, 1L, 3L, 3L, 3L, 3L, 3L, 3L, 3L),
     LU1.3 = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 4L, 4L, 4L, 4L,
     4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L), LU_tot = c(0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L,
     5L, 5L, 7L, 7L, 7L, 7L, 7L, 7L, 7L), LR_tot = c(1L, 1L, 1L,
     1L, 1L, 1L, 1L, 1L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L,
     5L, 5L, 5L, 5L, 5L, 5L, 5L), SP_tot = c(122L, 122L, 122L,
     122L, 122L, 122L, 122L, 122L, 61L, 61L, 61L, 61L, 61L, 61L,
     61L, 61L, 61L, 61L, 85L, 85L, 85L, 85L, 85L, 85L, 85L), SP1.1 = c(16L,
     16L, 16L, 16L, 16L, 16L, 16L, 16L, 3L, 3L, 3L, 3L, 3L, 3L,
     3L, 3L, 3L, 3L, 16L, 16L, 16L, 16L, 16L, 16L, 16L), SP1.2 = c(0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L), SP1.3 = c(23L, 23L,
     23L, 23L, 23L, 23L, 23L, 23L, 46L, 46L, 46L, 46L, 46L, 46L,
     46L, 46L, 46L, 46L, 32L, 32L, 32L, 32L, 32L, 32L, 32L), SP1.4 = c(45L,
     45L, 45L, 45L, 45L, 45L, 45L, 45L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 6L, 6L, 6L, 6L, 6L, 6L, 6L), SP_tot.1 = c(85L,
     85L, 85L, 85L, 85L, 85L, 85L, 85L, 50L, 50L, 50L, 50L, 50L,
     50L, 50L, 50L, 50L, 50L, 46L, 46L, 46L, 46L, 46L, 46L, 46L
     ), SO1.1 = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 5L, 5L, 5L, 5L, 5L, 5L, 5L),
     SO1.2 = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 1L, 1L, 1L, 1L,
     1L, 1L, 1L, 1L, 1L, 1L, 0L, 0L, 0L, 0L, 0L, 0L, 0L), SO1.3 = c(0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L), SO1.4 = c(0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     1L, 1L, 1L, 1L, 1L, 1L, 1L), SO_tot = c(1L, 1L, 1L, 1L, 1L,
     1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 6L, 6L,
     6L, 6L, 6L, 6L, 6L), SU1.1 = c(0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L, 0L, 0L), SU1.2 = c(2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L,
     3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 0L, 0L, 0L, 0L, 0L, 0L,
     0L), SU1.3 = c(16L, 16L, 16L, 16L, 16L, 16L, 16L, 16L, 3L,
     3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 16L, 16L, 16L, 16L, 16L,
     16L, 16L), SU_tot = c(19L, 19L, 19L, 19L, 19L, 19L, 19L,
     19L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 16L, 16L, 16L,
     16L, 16L, 16L, 16L), SR = c(17L, 17L, 17L, 17L, 17L, 17L,
     17L, 17L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 17L, 17L,
     17L, 17L, 17L, 17L, 17L)), .Names = c("P1", "P2", "P3", "P4",
"P5", "P6", "P8", "P9", "P10", "P11", "P12", "P7", "SITE", "Errors",
"warnings", "Manual", "Total", "H_tot", "HP1.1", "HP1.2", "HP1.3",
"HP1.4", "HP_tot", "HO1.1", "HO1.2", "HO1.3", "HO1.4", "HO_tot",
"HU1.1", "HU1.2", "HU1.3", "HU_tot", "HR", "L_tot", "LP1.1",
"LP1.2", "LP1.3", "LP1.4", "LP_tot", "LO1.1", "LO1.2", "LO1.3",
"LO1.4", "LO_tot", "LU1.1", "LU1.2", "LU1.3", "LU_tot", "LR_tot",
"SP_tot", "SP1.1", "SP1.2", "SP1.3", "SP1.4", "SP_tot.1", "SO1.1",
"SO1.2", "SO1.3", "SO1.4", "SO_tot", "SU1.1", "SU1.2", "SU1.3",
"SU_tot", "SR"), class = "data.frame", row.names = c(NA, -25L
))

I don't know if this could be a factor, but my data contains some weird 
characters.

Thanks everyone,
Stephane Vaucher

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
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> 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/


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