transform data assign value

[Michel Young]

Hi,
I started with the software (v12). I would like to know if it is possible to transform the values as shown below

my database is building with 107 columns and 1461 lines to represent date (tab1)
a date is associated with 106 data

I would like to reconstruct database to be
a date, a value , 1 concentration (tab2)

I tried to transform with long & wide format but the result does not match with what I want

I will be grateful for any comments and suggestions

date	amb1	bou1	gram1	bou3	gram3	gram5
01jan2012	.		.	.
02jan2012	.
03jan2012	.
04jan2012	.
05jan2012	.
06jan2012	.

tab2

date	taxon	concentration
01/01/12	bou1	.
01/01/12	gram1	.
01/01/12	bou3	.
01/01/12	gram3	.
01/01/12	gram5	.
02/01/12	bou1	.
02/01/12	gram1	.
02/01/12	bou3	.
02/01/12	gram3	.
02/01/12	gram5	.
03/01/12	bou1	.
03/01/12	gram1	.
03/01/12	bou3	.
03/01/12	gram3	.
03/01/12	gram5	.

[Joseph Coveney]

You probably will want your post to be in the General forum and not the Mata forum.

In the meantime, you could do something like the following.

foreach var of varlist _all {
    if "`var'" == "date" continue
    rename `var' concentration`var'
}
reshape long concentration, i(date) j(taxon) string

If your taxon variables are all ambl#, bou# and gram# (or a similar limited list), then you can use the multiple reshape command to add the prefix and avoid the explicit loop. See the help file for reshape for details.

[Michel Young]

great job ! thanks a lot for your help Joseph