How to expand?

[River Huang]

Suppose that I have the following data:

* Example generated by -dataex-. To install: ssc install dataex
clear
input str4 name float price str12 date float d
"A" 34 "2016-12-03" 20791
"A" 39 "2016-12-06" 20794
"A" 41 "2016-12-10" 20798
"B" 33 "2015-3-01"  20148
"B" 37 "2015-3-04"  20151
"B" 36 "2015-3-08"  20155
end
format %td d

I want to expand the data to obtain

* Example generated by -dataex-. To install: ssc install dataex
clear
input str4 name float price str12 date float d
"A" 34 "2016-12-03" 20791
"A" 34 "2016-12-06" 20792
"A" 34 "2016-12-06" 20793
"A" 39 "2016-12-06" 20794
"A" 39 "2016-12-10" 20795
"A" 39 "2016-12-10" 20796
"A" 39 "2016-12-10" 20797
"A" 41 "2016-12-10" 20798
"B" 33 "2015-3-01"  20148
"B" 33 "2015-3-04"  20149
"B" 33 "2015-3-04"  20150
"B" 37 "2015-3-04"  20151
"B" 37 "2015-3-08"  20152
"B" 37 "2015-3-08"  20153
"B" 37 "2015-3-08"  20154
"B" 36 "2015-3-08"  20155
end
format %td d

I use

expand d - d[_n-1]
sort name d
bys name (d): replace d = d[_n-1]+1 if _n > 1

But the observations on price are not what I had in mind. Basically, I want the price to remain the same until the next date that the price changes.

[William Lisowski]

I think this will do what you want.

sort name d // make sure they're sorted to begin with
expand d[_n+1]-d if name[_n+1]==name
sort name d // get the new ones sorted in with the old ones

[River Huang]

I think this will do what you want.

sort name d // make sure they're sorted to begin with
expand d[_n+1]-d if name[_n+1]==name
sort name d // get the new ones sorted in with the old ones

Dear William, Thanks a lot. It works well.