Javier,
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This is for v. 6...I can't imagine that v7 is different
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I think that it will probably be easiest if I just give you the steps with the functions & procs that I use. I am building some code at this moment and I glanced at it....it is dynamic with a lot of project specific objects so probably best to do it this way:
1) you have a group of time series items (lets say 1 year GDP growth for G10).
2) determine the date that you want to get a cross section for and turn that into an observation using @dtoo()
3) now, turn your group into a matrix using the stomna() proc. This brings in any NA's so that you can match up your observation number with a row in the matrix.
4) You have a matrix and you have an observation number. Now pull out the row of the matrix into a vector using @rowextract().
Vector {%Vector} = @transpose(@rowextract(TmpMtx, !lastObs))
above I created a column vector by transposing the row from the matrix.
5) this is either your x data or your y data. Repeat steps 1-4 above to get the data for the other side of the xy pair (for simplicity you could compare to an earlier data in your time series to see how growth momentum compares).
6) you should now have two vectors. create a blank matrix to hold the two data vectors. that should be column vectors with equal dimensions. so use something like:
matrix(@rows({%xvector}), 2) TmpMtx
7) you now have a matrix called TmpMtx with two columns and the same number of rows as your two xy column vectors. put the vectors in the matrix:
colplace(TmpMtx, {%xvector}, 1) 'putting the xvector in the 1st column of the TmpMtx
colplace(TmpMtx, {%yvector}, 2) 'putting the yvector in the 2nd column of the TmpMtx

you've now got TmpMtx with two columns and you can use the various charting features as you've already done in other posts.
I used:
freeze({%gph}) TmpMtx.scat linefit
All of this seems a little cumbersome at first but as you get used to using the method, it becomes VERY useful. I use the basic idea of this technique for all sorts of time dynamic calculations.
hope that is helpful.
Steve
p.s. be sure to clean up your objects along the way. if you are doing multiple graphs this can make a mess in your workfile.