[R] Wilcox paired test error message

[Sarah Goslee]

Hi,

If you're doing exactly as described below, then you need to add the
data argument to wilcox.test so R knows where to find beforesmall and
aftersmall. But if so, that's a rather uninformative error message.

Saraj

On Sun, Jun 23, 2013 at 2:34 PM, ruth parker <parkeractonruth at gmail.com> wrote:
> Hi,
> I've been trying to run a wilcox paired test on some data
>  beforesmall aftersmall
>  [1,]        63.5      512.0
>  [2,]        54.5      237.5
>  [3,]        52.5      161.5
>  [4,]        78.0      153.5
>  [5,]        53.5       68.0
>  [6,]        50.5       65.5
>  [7,]        69.0       52.0
>  [8,]        76.0       59.0
>  [9,]        68.0       66.5
> [10,]        75.5       66.5
> [11,]        67.0       45.5
> [12,]        81.0       54.5
> [13,]        49.0       44.0
> [14,]        51.0       42.5
> [15,]        53.0       34.5
>
> using
> wilcox.test(beforesmall ~ aftersmall,paired=T)
> but I get the error message:
>
> Error in wilcox.test.formula(beforesmall ~ aftersmall, paired = T) :
>   grouping factor must have exactly 2 levels
>
> I don't have any missing values, I have the same amount of data points for
> each group and I've looked everywhere trying to find the answer.
> Please can somebody tell me how to make it work
> thanks
>

-- 
Sarah Goslee
http://www.functionaldiversity.org