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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
RE: st: How do i substitute the return local of program in the if expression of the egen command? |

Date |
Tue, 30 Mar 2010 13:36:35 +0100 |

Several questions are bundled up together here at different levels. Let me try to separate them. Let's put aside questions about ` ' (right) and ' ' (wrong) on one side as understood. 1. The underlying problems ========================== Antonis wants the row total of variables if and only if all variables are zero or positive. Otherwise put: if the row minimum is zero or positive. Given the second formulation, no program is needed: egen rowmin = rowmin(<varlist>) egen rowtotal = rowtotal(<varlist>) if rowmin >= 0 Antonis' other code looks like more -egen- calls once he's done this. Correct me if I'm wrong. 2. Why a call to r() didn't work initially ========================================== Maarten explained this. Antonis wants the incarnation of his r() result as a local macro and must use ` ' to get its contents. 3. Why the second call to r() still does not work ================================================= This is more subtle. The first call to -egen- internally calls -count-. A side-effect of that is that existing r() results are zapped. Thus by the time of his second -egen- call the r() result Antonis wants no longer exists. He is then calling -egen- with an empty -if- condition, which is illegal. 4. What could be done instead ============================= If you wanted to program this, and didn't like the solution in #1 for some reason, it is better to join the two programs into one based on something like gen rowtotal = 0 foreach v of local varlist { replace rowtotal = rowtotal + cond(`v' >= 0, `v', .) } Adding one missing whenever a variable is negative should be sufficient to get the result desired. Antonis had a helper program that given (say) local varlist var1 var2 var3 var4 var5 produces var1 >= 0 & var2 >= 0 & var3 >= 0 & var4 >= 0 & var5 >= 0 There are tricks to do that more directly. local cond : subinstr local varlist " " ">= 0 & ", all local cond `cond' >= 0 That is, replace each internal space by ">= 0 &" and then append a final ">= 0". Nick n.j.cox@durham.ac.uk Martin Weiss set trace on then, and see where the thing goes awry, i.e. post the lines surrounding the error... A Loumiotis Sorry.... I mistyped the wrong left single quotation mark in my email reply, but in my code I used the correct left quotation mark "`" and I still get for the !(`r(andpve)') if expression invalid syntax r(198); Martin Weiss > Seems the left single quote is not correct. Replace "'" with "`", w/o the > quotation marks, of course... A Loumiotis > Thanks for your help! > > using `r(andpve)' resolves the first problem... > > but for !('r(andpve)') i get the following > > invalid syntax > r(198); Maarten buis A Loumiotis wrote: >>> I have written a program (with the name andpve) that >>> generates an expression of the form: >>> >>> var1>=0 & var2>=0 & ... & varN>=0 >>> >>> and returns this value as a local with name r(andpve). >>> >>> I then want to use r(andpve) in another progam (rowctotal) >>> where U substitute it in the if expression of the egen command. >>> >>> egen `left'_a = rowtotal(`right') if r(andpve), missing >>> egen `left'_b = rowmin(`right') if !(r(andpve)) >> >> egen `left'_a = rowtotal(`right') if `r(andpve)', missing >> egen `left'_b = rowmin(`right') if !(`r(andpve)') >>> But the egen command does not seem understand the r(andpve) >>> as an if >>> expression or the !(r(andpve)) as an if expression. >>> >>> What did I do wrong? I'm new to Stata. The code is >>> below. > >>> program rowctotal, rclass >>> version 11 >>> gettoken left right: 0 >>> capture drop `left' >>> andpve `right' >>> di r(andpve) >>> egen `left'_a = rowtotal(`right') if r(andpve), >>> missing >>> egen `left'_b = rowmin(`right') if !(r(andpve)) >>> egen `left' = rowtotal(`left'_*), missing >>> *drop `left'_* >>> end >>> >>> program andpve, rclass >>> local k = 1 >>> while "``k''" != "" { >>> local ++k >>> } >>> local --k >>> local i = 1 >>> local andpve "" >>> while `i' <= `k'-1 { >>> local andpve "`andpve'``i''>=0 & " >>> local ++i >>> } >>> local andpve "`andpve'``i''>=0" >>> return local andpve `andpve' >>> end >>> * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: How do i substitute the return local of program in the if expression of the egen command?***From:*A Loumiotis <antonis.loumiotis@gmail.com>

**References**:**st: How do i substitute the return local of program in the if expression of the egen command?***From:*A Loumiotis <antonis.loumiotis@gmail.com>

**Re: st: How do i substitute the return local of program in the if expression of the egen command?***From:*Maarten buis <maartenbuis@yahoo.co.uk>

**Re: st: How do i substitute the return local of program in the if expression of the egen command?***From:*A Loumiotis <antonis.loumiotis@gmail.com>

**Re: st: How do i substitute the return local of program in the if expression of the egen command?***From:*A Loumiotis <antonis.loumiotis@gmail.com>

**AW: st: How do i substitute the return local of program in the if expression of the egen command?***From:*"Martin Weiss" <martin.weiss1@gmx.de>

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