Mean of frequency from tab

[Johannes Schuett]

Hello,
i'm using Stata 16.

I am trying to calculate the mean of the frequency values (second column) of a tab result:

. tab bin if year == 2005

        bin |      Freq.     Percent        Cum.
------------+-----------------------------------
      -97.5 |          6        0.26        0.26
      -94.5 |          4        0.17        0.43
      -91.5 |         10        0.43        0.86
      -88.5 |         10        0.43        1.28
      -85.5 |          9        0.39        1.67
      -82.5 |          6        0.26        1.93
      -79.5 |         10        0.43        2.35
      -76.5 |         14        0.60        2.95
      -73.5 |         11        0.47        3.42
      -70.5 |         22        0.94        4.37
      -67.5 |         12        0.51        4.88
      -64.5 |         20        0.86        5.74
      -61.5 |         18        0.77        6.51
      -58.5 |         22        0.94        7.45
      -55.5 |         21        0.90        8.35
      -52.5 |         22        0.94        9.29
      -49.5 |         29        1.24       10.53
      -46.5 |         35        1.50       12.03
      -43.5 |         31        1.33       13.36
      -40.5 |         18        0.77       14.13
.
.
.
------------+-----------------------------------
      Total |      2,336      100.00

I found out that I can save my results in a matrix using the command

tab bin if year == 2005, matcell(freqs)

but I don't know if that's going to get me anywhere.

[Nick Cox]

The mean frequency is just the total count divided by the number of bins.

count if bin < . &  year == 2005
local N = r(N)
tab bin if year == 2005
di `N' / r(r)

I suspect that you want, or need, something quite different, possibly starting with

contract bin year

[Dirk Enzmann]

sysuse auto, clear

tabulate rep78, matcell(F)
matlist F
mata: st_numscalar("r(mf)",mean(st_matrix("F")))
di "Mean frequencies = `r(mf)'"

Result:

. di "Mean frequencies = `r(mf)'"
Mean frequencies = 13.8

After reading Nick's post:

sysuse auto, clear
tabulate rep78
di "Mean frequencies = " r(N)/r(r)