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From |
Eric Booth <eric.a.booth@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Generate random missing values within a set of variables |

Date |
Sun, 15 Apr 2012 12:08:41 -0500 |

<> Others have offered solutions with the data in wide format, here's another approach after reshaping to long (to me, this is an easier approach): *******************! watch for wrapping below: *-- make some fake data clear set obs 1000 forvalues i =1/6{ gen x`i' = rnormal() } g i = _n reshape long x, i(i) j(j) tempvar rand rand2 *--1. "I would like to randomly generate one missing value in one of the 6 variables per line/observation" bys i: gen `rand' = runiform() bys i (`rand'): gen missingone = j if _n==1 *--2. "then in another set of variables randomly generate 2 missing values per line/observation - 2 out of the 6 variables" bys i: gen `rand2' = runiform() bys i (`rand2'): gen missingtwo = j if inlist(_n, 1, 2) *--3. Make one or two values missing, as described clonevar x_two = x //x_two is for your second condition (2 missing values per group) lab var x_two "same as x, but will have 2 missing obs per group" replace x = . if !mi(missingone) replace x_two = . if !mi(missingtwo) sort i j ta miss* *--reshape back if you want this data to be wide again drop __* missing* reshape wide x* , i(i) j(j) *******************! - Eric __ Eric A. Booth Public Policy Research Institute Texas A&M University ebooth@ppri.tamu.edu +979.845.6754 On Apr 15, 2012, at 7:06 AM, Sofia Ramiro wrote: > Dear all, > > I have 6 variables (without missings) and I would like to randomly generate one missing value in one of the 6 variables per line/observation (and then in another set of variables randomly generate 2 missing values per line/observation - 2 out of the 6 variables). > I know that with the runiform command we manage to choose observations randomly within one variable (so I could generate random missing values within one variable), but how can I choose randomly one variable out of the 6 to be transformed into missing and make sure that one of them is being transformed per observation? > > I appreciate your help. > > Thanks! > > Sofia > > * > * 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/ * * 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: Generate random missing values within a set of variables***From:*Sofia Ramiro <sofiaramiro@hotmail.com>

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