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From |
Nick Cox <njcoxstata@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Renaming variables using foreach |

Date |
Tue, 26 Jun 2012 22:45:59 +0100 |

Working backwards, 0. Your example sounds like a very bad idea. Your variables have names that mean something; you want instead to impose arbitrary and meaningless names. I am reminded of learning MINITAB some decades ago and finding that I could call my columns [sic] anything I wanted so long as it was something like C1, C2, C3.... (At least that it is what I recall.) 1. In Stata 12, -rename- is now so versatile that writing your own -foreach- loop shouldn't be necessary for renaming. 2. Personally, I still tend to reach for -renvars- (SJ) because I internalised most of the syntax over ten years of using it. 3. What's wrong with your -foreach- loop? local i = `i' + 1 foreach x of varlist <whatever> { rename `x' var`i' } Evidently local macro -i- was not mentioned before this code. Thus you define local i = `i' + 1 On the right-hand side you reference a local macro which does not yet exist. That is OK by Stata. It merely subsitutes the references by nothing. The expression now reads local i = +1 which is OK by Stata. It does the arithmetic, +1 evaluates to 1, and the local macro -i- is born as the string "1". For all the difference it makes, you could have written local i "1" or local i = 1 The crucial point is this. You've defined the local macro once, but once in the loop you never change it. (So, this bites second time around the loop, when -rename- to -var1- fails because -var1- already exists.) Or, to put it more directly, the local macro (re-)definition belongs _inside_ the loop, so that the incrementation takes place as you want (and need). foreach x of varlist <whatever> { local i = `i' + 1 rename `x' var`i' } Nick On Tue, Jun 26, 2012 at 10:20 PM, Suryadipta Roy <sroy2138@gmail.com> wrote: > I am currently learning looping in Stata and is stuck with the > following problem: I have about 150 variables that I want to rename as > var1 var2, etc.. upto var 150. I tried the following: > > local i = `i' + 1 > foreach x of varlist Agricultural_raw_materials_expor - > Value_lost_due_to_electrical_out { > 2. rename `x' var`i' > 3. } > > I am getting the following error message: > var1 already defined > r(110); > > I find that only the first variable is renamed as "var1" and then the > loop stopped running. Any help is greatly appreciated. * * 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/

**References**:**st: Renaming variables using foreach***From:*Suryadipta Roy <sroy2138@gmail.com>

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