Dear Nick,
thanks very much already! but unfortunately it didn't work yet with your program, I get an error message "invalid syntax" already after the line
"program polyarea, rclass"
I am using version 7, could this cause the problem?
Do I need the part about missing values, even if there are no missing in my data?
Has "varlist" to be replace by my x and y variables, too?
Below is the do-file I used, adapted to the data set I attached as well:
Would be great, if you could have a look at it!
Thanks!
Dietrich.
_______________________________________________
*polyarea xvar yvar [in]
*belongs to program?
*! NJC 1.0.0 15 August 2003
program polyarea, rclass
version 7
syntax varlist(min=2 max=2 numeric) [in]
tokenize `varlist'
args v1 v2
marksample touse, novarlist
qui count if `touse' & (missing(`v1') | missing(`v2'))
if r(N) {
di as err "missing values in data"
exit 198
}
tempvar order area
gen long `order' = _n
su `order' if `touse', meanonly
qui gen `area' = `touse' * ///
(`v1'[_n + 1] - `v1') * (`v2'[_n + 1] + `v2') / 2
qui replace `area' = ///
(`v1'[`r(min)'] - `v1') * (`v2'[`r(min)'] + `v2') / 2 in `r(max)'
su `area', meanonly
di as res %9.0g abs(r(sum))
return scalar area = abs(r(sum))
end
______________________________________________
[email protected] schrieb am 26.11.03 14:33:00:
>
> I found this in my files. No help file
> was written. It does the area bit.
>
> Feed it the x and y coordinates of the
> polygon vertices. The syntax is
>
> polyarea xvar yvar [in]
>
> *! NJC 1.0.0 15 August 2003
> program polyarea, rclass
> version 8
> syntax varlist(min=2 max=2 numeric) [in]
>
> tokenize `varlist'
> args x y
>
> marksample touse, novarlist
> qui count if `touse' & (missing(`x') | missing(`y'))
> if r(N) {
> di as err "missing values in data"
> exit 198
> }
>
> tempvar order area
>
> gen long `order' = _n
> su `order' if `touse', meanonly
>
> qui gen `area' = `touse' * ///
> (`x'[_n + 1] - `x') * (`y'[_n + 1] + `y') / 2
> qui replace `area' = ///
> (`x'[`r(min)'] - `x') * (`y'[`r(min)'] + `y') / 2 in `r(max)'
> su `area', meanonly
>
> di as res %9.0g abs(r(sum))
> return scalar area = abs(r(sum))
> end
>
> Nick
> [email protected]
>
>
~~~~~~~~~~~~~~~~~~~~~~~~
Dietrich�Dr�ner
Schneckenburgstr.�24
D�-�78467�Konstanz
Tel.�(+49)�-�7531�-�698003
Fax�(+49)�-�1212�-�522970813
Mob.(Inland):�(+49)�-�177�-�6334099
Mob.(Ausland):(+49)�-�162�-�7679952
~~~~~~~~~~~~~~~~~~~~~~~~
Attachment:
cmcored98134.dta
Description: Binary data
