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From |
Rebecca Pope <rebecca.a.pope@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: How can I get the second last non-missing value? |

Date |
Thu, 13 Jun 2013 09:13:00 -0500 |

Any time I would have saved by using Mata would have been completely lost to time figuring out how to accomplish it in Mata. Sergiy, would you mind providing a little explanation for what your code is doing? I made some notes below about what I think is going on, but I just want to make sure I'm following you. *** mata void prelast() { <= like -capture program drop-?, you're just clearing out any previous definition of the program? V=. <= define a null matrix V st_view(V,.,st_local("varlist")) <= make a view onto the data (presumably here to save memory?), all observations on the variables given in the Stata local macro varlist (supplied elsewhere) R=. st_view(R,.,st_local("result")) <= this bit confused me at first b/c I thought the variable had to exist already, but you handle this by generating a result variable with all values missing before you run prelast(), correct? for(i=1;i<=rows(V);i++) { <= loosely, for every observation in the dataset for(j=0;j<cols(V);j++) { <= loosely, for all variables given in `varlist' except the last one if (missing(V[i,cols(V)-j])==0) { <= j is increasing so the column index here is decreasing, in effect, counting backwards // found last non-missing if (cols(V)-j-1<1) break; //nothing before for(k=cols(V)-j-1;k>=1;k--) { <= lost me here, why increment k, don't you know you want cols(V)-j-1 since cols(V)-j is the last non-missing value? if (missing(V[i,k])==0) R[i,1]=V[i,k] <= replace the ith observation (row) in the R vector with the appropriate value from V break; } break; } } } } end *** Thanks, Rebecca < snip > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: How can I get the second last non-missing value?***From:*Sergiy Radyakin <serjradyakin@gmail.com>

**References**:**st: How can I get the second last non-missing value?***From:*duygu yıldırım <dyg_math@hotmail.com>

**Re: st: How can I get the second last non-missing value?***From:*Rebecca Pope <rebecca.a.pope@gmail.com>

**Re: st: How can I get the second last non-missing value?***From:*Sergiy Radyakin <serjradyakin@gmail.com>

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