[R] Use of results in summary

[Mark Myatt]

Patrick Buetzberger <patrick at giub.unibe.ch> writes:

>When making a summary with a vector, the result is "numeric" and I can
>recall its components (like median, mean, etc.) for further use.
>However, if I use summary with a matrix, the result is of mode
>"character" (like  "Median : 1.2127") and I cannot extract the results
>for direct further use.
>Thanks for any hints,

That is annoying ... but you can take advantage of the output format
(i.e. label separated from value by a colon) to extract what you want
using strsplit() and unlist():

        > my.matrix <-matrix(c(1,2,3,4,5,6), nrow = 2, ncol = 3)
        > my.matrix
             [,1] [,2] [,3]
        [1,]    1    3    5
        [2,]    2    4    6
        > x <- summary(my.matrix)
        > x
               X1             X2             X3      
         Min.   :1.00   Min.   :3.00   Min.   :5.00  
         1st Qu.:1.25   1st Qu.:3.25   1st Qu.:5.25  
         Median :1.50   Median :3.50   Median :5.50  
         Mean   :1.50   Mean   :3.50   Mean   :5.50  
         3rd Qu.:1.75   3rd Qu.:3.75   3rd Qu.:5.75  
         Max.   :2.00   Max.   :4.00   Max.   :6.00  
        > x[1,3]
        [1] "Min.   :5.00  "
        > as.numeric(unlist(strsplit(x[1,3], ":"))[2])
        [1] 5

BUT ... you could always apply() to extract just the summary you want:

        > apply(my.matrix, 2, median)
        [1] 1.5 3.5 5.5

And do away with summary() and the as.numeric(unlist(strsplit())[])
business altogether ... a better solution,  I think.

Hope that helps,

Mark


--
Mark Myatt


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