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

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

Subject |
st: RE: count non-missing elements in a series |

Date |
Thu, 25 Mar 2004 10:24:01 -0000 |

You don't give a very clear idea of your data structure. I guess that you have panel data, something like . tsset country year and a series of variables for different industries, say industry1-industry10 What you want in question 1 can be got in various ways. Here is one: The first value for each panel is 1 if the investment value is not missing and 0 otherwise: . by id : gen nrun = !mi(industry1) if _n == 1 Subsequent values are always 0 if the investment value is missing and 1 greater than the previous otherwise. . by id : replace nrun = cond(mi(industry1), 0, nrun[_n-1] + 1) if _n > 1 Another way of doing it is to use -tsspell- from SSC. Install that by . ssc inst tsspell Then for say -industry1- the definition of a spell is just a sequence of non-missing values of -industry1-. . tsspell, c(industry1 < .) The variable _seq created by -tsspell- is what you want. Spells automatically are determined separately by panel. If different industries have different patterns of missing values, you would need something more like this: forval i = 1/10 { tsspell, c(industry`i' < .) spell(_spell`i') seq(_seq`i') end(_end`i') } After which you might want to -drop- some of the created variables. Nick n.j.cox@durham.ac.uk Oleksandr Shepotylo > > I am using perpetual inventory method to calculate > capital stock but my > dataset has a lot of missing data on investment. I have two questions: > > 1. For any given country and industry, I want to create > an index that > will tell me how many > non-missing numbers in a row I have prior to any year t. > For example, I have investment data for country i and > industry j starting > from 1965 to 1975 then missing in 1976-1977 and continuing in > 1978-2001. The > index should start from 1 in 1965 till 11 in 1975. then it equals 0 in > 1976-1977 and starts from 1 again in 1978. > > 2. Less important, but still interesting. How to impute > missing data if > the gap- like in previous example- is less or equal to 2? > Imputation can be > based on average growth in capital stock for last 3 years. * * 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/

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