Counting specific observations satisfying conditions

[Fabio Delisio]

Hi,
I have a dataset with 4122 observations, and I have to count the number of commodities and markets in every year (2014, 2015 and 2016).
To explain better the issue, a question is "How many observations of "Cowpeas" are in 2015? And in which market?"

Is it possible to do it?
Thanks.

* Example generated by -dataex-. For more info, type help dataex
clear
input str39 market str46 commodity int year float price
"Alto Molócuè" "Sugar (brown local) "             2016      50
"Alto Molócuè" "Cowpeas"                          2014      15
"Alto Molócuè" "Cowpeas"                          2015      15
"Alto Molócuè" "Rice (local)"                     2014       .
"Alto Molócuè" "Rice (imported)"                  2014      25
"Alto Molócuè" "Beans (magnum)"                   2016      70
"Alto Molócuè" "Maize meal (white without bran) " 2015       .
"Alto Molócuè" "Cassava flour"                    2015      10
"Alto Molócuè" "Groundnuts (small shelled) "      2014 26.6667
"Alto Molócuè" "Oil (vegetable imported) "        2016       .
"Alto Molócuè" "Groundnuts (small shelled) "      2014      25
"Alto Molócuè" "Groundnuts (large shelled) "      2016       .
"Alto Molócuè" "Beans (red)"                      2015    37.5
"Alto Molócuè" "Maize (white)"                    2015       9
"Alto Molócuè" "Rice (imported)"                  2015    27.5
"Alto Molócuè" "Rice (imported)"                  2015   25.25
"Alto Molócuè" "Maize meal (white first grade) "  2016 66.6667
"Alto Molócuè" "Maize meal (white without bran) " 2014    22.5
"Alto Molócuè" "Wheat flour (local)"              2016 40.6667
"Alto Molócuè" "Maize meal (white with bran) "    2016 21.6667
"Alto Molócuè" "Beans (red)"                      2015       .
"Alto Molócuè" "Sugar (brown local) "             2015       .
"Alto Molócuè" "Maize meal (white with bran) "    2015       .
"Alto Molócuè" "Sugar (brown local) "             2014      39
"Alto Molócuè" "Beans (catarino)"                 2016       .
"Alto Molócuè" "Sugar (brown local) "             2016 63.3333
"Alto Molócuè" "Groundnuts (large shelled) "      2015       .
"Alto Molócuè" "Cassava flour"                    2016      12
"Alto Molócuè" "Beans (magnum)"                   2016       .
"Alto Molócuè" "Sugar (brown imported) "          2016       .
"Alto Molócuè" "Cowpeas"                          2016       .
"Alto Molócuè" "Sugar (brown local) "             2015       .
"Alto Molócuè" "Rice (local)"                     2016      35
"Alto Molócuè" "Beans (magnum)"                   2016       .
"Alto Molócuè" "Maize meal (white with bran) "    2014       .
"Alto Molócuè" "Cassava flour"                    2015  9.3333
"Alto Molócuè" "Rice (imported)"                  2016 51.3333
"Alto Molócuè" "Cowpeas"                          2016      30
"Alto Molócuè" "Oil (vegetable imported) "        2015       .
"Alto Molócuè" "Oil (vegetable imported) "        2016       .
"Alto Molócuè" "Sugar (brown imported) "          2016       .
"Alto Molócuè" "Groundnuts (small shelled) "      2016     125
"Alto Molócuè" "Maize meal (white without bran) " 2016      50
"Alto Molócuè" "Maize meal (white without bran) " 2016      35
"Alto Molócuè" "Beans (dry)"                      2014    32.5
"Alto Molócuè" "Rice (imported)"                  2014      25
"Alto Molócuè" "Cowpeas"                          2014   16.25
"Alto Molócuè" "Maize (white)"                    2015  8.3429
"Alto Molócuè" "Cassava flour"                    2014       .
"Alto Molócuè" "Cowpeas"                          2015       .
"Alto Molócuè" "Maize meal (white first grade) "  2015       .
"Alto Molócuè" "Groundnuts (large shelled) "      2015    27.5
"Alto Molócuè" "Oil (vegetable local) "           2016 81.6667
"Alto Molócuè" "Beans (catarino)"                 2016      60
"Alto Molócuè" "Oil (vegetable imported) "        2016       .
"Alto Molócuè" "Maize meal (white with bran) "    2015      12
"Alto Molócuè" "Maize meal (white first grade) "  2015      40
"Alto Molócuè" "Wheat flour (local)"              2014      22
"Alto Molócuè" "Cassava flour"                    2015      10
"Alto Molócuè" "Sugar (brown local) "             2015       .
"Alto Molócuè" "Sugar (brown local) "             2015       .
"Alto Molócuè" "Groundnuts (small shelled) "      2014      50
"Alto Molócuè" "Groundnuts (large shelled) "      2015      20
"Alto Molócuè" "Oil (vegetable local) "           2015    67.5
"Alto Molócuè" "Groundnuts (large shelled) "      2014    42.5
"Alto Molócuè" "Sugar (brown imported) "          2015      39
"Alto Molócuè" "Maize meal (white with bran) "    2014   12.75
"Alto Molócuè" "Cowpeas"                          2014 23.3333
"Alto Molócuè" "Wheat flour (local)"              2014 21.3333
"Alto Molócuè" "Rice (imported)"                  2015      25
"Alto Molócuè" "Maize meal (white first grade) "  2015      40
"Alto Molócuè" "Maize meal (white without bran) " 2014 15.6667
"Alto Molócuè" "Rice (local)"                     2015      31
"Alto Molócuè" "Maize (white)"                    2015 14.8571
"Alto Molócuè" "Sugar (brown local) "             2014      38
"Alto Molócuè" "Groundnuts (large shelled) "      2015    37.5
"Alto Molócuè" "Maize meal (white first grade) "  2014   36.67
"Alto Molócuè" "Rice (local)"                     2015    29.4
"Alto Molócuè" "Maize meal (white first grade) "  2016      35
"Alto Molócuè" "Sugar (brown imported) "          2016       .
"Alto Molócuè" "Maize meal (white without bran) " 2014      20
"Alto Molócuè" "Oil (vegetable local) "           2016     140
"Alto Molócuè" "Maize meal (white with bran) "    2016    24.5
"Alto Molócuè" "Sugar (brown local) "             2014   35.67
"Alto Molócuè" "Beans (catarino)"                 2016      80
"Alto Molócuè" "Rice (local)"                     2016      30
"Alto Molócuè" "Maize meal (white first grade) "  2014 36.1111
"Alto Molócuè" "Groundnuts (small shelled) "      2016       .
"Alto Molócuè" "Maize meal (white without bran) " 2016       .
"Alto Molócuè" "Cassava flour"                    2015      11
"Alto Molócuè" "Cowpeas"                          2014      15
"Alto Molócuè" "Oil (vegetable imported) "        2014       .
"Alto Molócuè" "Groundnuts (large shelled) "      2016     130
"Alto Molócuè" "Maize (white)"                    2015  9.5714
"Alto Molócuè" "Rice (local)"                     2015    33.5
"Alto Molócuè" "Maize meal (white first grade) "  2016      80
"Alto Molócuè" "Cassava flour"                    2014       .
"Alto Molócuè" "Groundnuts (large shelled) "      2015      31
"Alto Molócuè" "Oil (vegetable local) "           2016      80
"Alto Molócuè" "Beans (butter)"                   2016      70
end

[Carlo Lazzaro]

Fabb:
welcome to this forum.
Something like:

bysort year market: egen wanted=total(commodity) if commodity=="oneofyourcommodities"

[Nick Cox]

Unfortunately. @Carlo Lazzaro's suggestion in #2 won't work as total() can't digest a string variable.

You can do something like

table (commodity) (market) (year)

or with groups from the Stata Journal

. groups market commodity year 

  +--------------------------------------------------------------------------+
  |       market                          commodity   year   Freq.   Percent |
  |--------------------------------------------------------------------------|
  | Alto Molócuè                     Beans (butter)   2016       1      1.00 |
  | Alto Molócuè                   Beans (catarino)   2016       3      3.00 |
  | Alto Molócuè                        Beans (dry)   2014       1      1.00 |
  | Alto Molócuè                     Beans (magnum)   2016       3      3.00 |
  | Alto Molócuè                        Beans (red)   2015       2      2.00 |
  |--------------------------------------------------------------------------|
  | Alto Molócuè                      Cassava flour   2014       2      2.00 |
  | Alto Molócuè                      Cassava flour   2015       4      4.00 |
  | Alto Molócuè                      Cassava flour   2016       1      1.00 |
  | Alto Molócuè                            Cowpeas   2014       4      4.00 |
  | Alto Molócuè                            Cowpeas   2015       2      2.00 |
  |--------------------------------------------------------------------------|
  | Alto Molócuè                            Cowpeas   2016       2      2.00 |
  | Alto Molócuè        Groundnuts (large shelled)    2014       1      1.00 |
  | Alto Molócuè        Groundnuts (large shelled)    2015       5      5.00 |
  | Alto Molócuè        Groundnuts (large shelled)    2016       2      2.00 |
  | Alto Molócuè        Groundnuts (small shelled)    2014       3      3.00 |
  |--------------------------------------------------------------------------|
  | Alto Molócuè        Groundnuts (small shelled)    2016       2      2.00 |
  | Alto Molócuè                      Maize (white)   2015       4      4.00 |
  | Alto Molócuè    Maize meal (white first grade)    2014       2      2.00 |
  | Alto Molócuè    Maize meal (white first grade)    2015       3      3.00 |
  | Alto Molócuè    Maize meal (white first grade)    2016       3      3.00 |
  |--------------------------------------------------------------------------|
  | Alto Molócuè      Maize meal (white with bran)    2014       2      2.00 |
  | Alto Molócuè      Maize meal (white with bran)    2015       2      2.00 |
  | Alto Molócuè      Maize meal (white with bran)    2016       2      2.00 |
  | Alto Molócuè   Maize meal (white without bran)    2014       3      3.00 |
  | Alto Molócuè   Maize meal (white without bran)    2015       1      1.00 |
  |--------------------------------------------------------------------------|
  | Alto Molócuè   Maize meal (white without bran)    2016       3      3.00 |
  | Alto Molócuè          Oil (vegetable imported)    2014       1      1.00 |
  | Alto Molócuè          Oil (vegetable imported)    2015       1      1.00 |
  | Alto Molócuè          Oil (vegetable imported)    2016       3      3.00 |
  | Alto Molócuè             Oil (vegetable local)    2015       1      1.00 |
  |--------------------------------------------------------------------------|
  | Alto Molócuè             Oil (vegetable local)    2016       3      3.00 |
  | Alto Molócuè                    Rice (imported)   2014       2      2.00 |
  | Alto Molócuè                    Rice (imported)   2015       3      3.00 |
  | Alto Molócuè                    Rice (imported)   2016       1      1.00 |
  | Alto Molócuè                       Rice (local)   2014       1      1.00 |
  |--------------------------------------------------------------------------|
  | Alto Molócuè                       Rice (local)   2015       3      3.00 |
  | Alto Molócuè                       Rice (local)   2016       2      2.00 |
  | Alto Molócuè            Sugar (brown imported)    2015       1      1.00 |
  | Alto Molócuè            Sugar (brown imported)    2016       3      3.00 |
  | Alto Molócuè               Sugar (brown local)    2014       3      3.00 |
  |--------------------------------------------------------------------------|
  | Alto Molócuè               Sugar (brown local)    2015       4      4.00 |
  | Alto Molócuè               Sugar (brown local)    2016       2      2.00 |
  | Alto Molócuè                Wheat flour (local)   2014       2      2.00 |
  | Alto Molócuè                Wheat flour (local)   2016       1      1.00 |
  +--------------------------------------------------------------------------+

The frequencies themselves can come from

bysort commodity market year : gen count = _N 

[Fabio Delisio]

Thank to both of you for the answers. In fact, @Carlo Lazzaro's code gives me a "type mismatch" error.
The "table" code seems perfect for my analysis.