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From |
jpitblado@stata.com (Jeff Pitblado, StataCorp LP) |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: the -missing- command |

Date |
Mon, 10 Oct 2005 16:34:25 -0500 |

louis boakye-yiadom <louisby@hotmail.com> asks about the -missing()- function: > I have two questions regarding the -missing- command (or function?). > First question: > I'm not clear about exactly what -missing- does. An example will clarify my > concern. I have a dataset containing 11 variables (the first is -clust- and > the last is -s11aq13-). One of the variables is -trexpcd-, and the total > number of observations is 4872. I gave the following commands and had the > shown output: > count if mi(trexpcd) > 4649 > count if mi(clust-s11aq13) > 82 > My understanding of the online -help- is that -missing- evaluates the number > of observations for which any of the arguments is missing. So, for the > second command, since -trexpcd- is one of the arguments, I expected the > result to be a number which is at least equal to 4649. > Can anyone please show me what I'm missing? > Second question: > Also, I had the following result: > count if !mi(clust-s11aq13) > 4790 > Does !mi() evaluate the number of observations for which none of the > arguments is missing? Thank you. I believe what Louis wants is Nick Cox's -nmissing- command, which (among other things) reports the number of missing values found in the variable of the dataset: . ssc install nmissing (output omitted) . sysuse auto (1978 Automobile Data) . nmissing rep78 5 . There is also a companion command called -npresent- that reports the number of non-missing values found in each variable of the dataset: . npresent make 74 price 74 mpg 74 rep78 69 headroom 74 trunk 74 weight 74 length 74 turn 74 displacement 74 gear_ratio 74 foreign 74 Also, look into the -mark- and -markout- commands. They help you generate a variable that indicates observations that are free of missing values for a specified list of variables: . mark touse . markout touse price-foreign . count if touse 69 Svend Juul <SJ@SOCI.AU.DK> also replied and was puzzled by the results of the following commands: . count if missing(rep78-headroom) 5 . count if missing(mpg-headroom) 0 -missing()- is a function, in this context "rep78-headroom" is interpreted to mean the difference between the variables -rep78- and -headroom-. --Jeff jpitblado@stata.com * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: the -missing- command***From:*"louis boakye-yiadom" <louisby@hotmail.com>

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