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From |
Christophe Kolodziejczyk <ck.statalist@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Mata Data Structure or "variable" variable names for timeseries computations |

Date |
Thu, 2 Aug 2012 17:07:41 +0200 |

I think one solution is to use a vector of pointers where you store the adresses of your matrices. Then you can compute first differences with a loop over this vector. As suggested by Tirthankar, another way is to pool all your datasets and treat it like a panel with year is the identifier. Then you can create a function which computes the first differences. See the Panelsetup() in the mata manual in order to do this. Hope this helps Christophe 2012/8/1 Matthew McKay <matthew.mckay@anu.edu.au>: > Dear StataList, > > I am trying to compute differences in sets of matrices matrices using MATA > for a time series 1995 to 2010. > I am producing a mata function to compute the differences for each year > after I load in ALL my yearly data matrices. > My Issue is in Step#2 is that I want to use a similar methodology to local > macro's in do files. (which can't be done) > > How can I pass part of a variable name (like Year) into the function and > then perform a set of computations over the data that is loaded in MATA? > In MATA how can you cycle through different variables (substituting in > different year append) and compute a new set of matrices? > Should I be constructing a Struct that contains a Data Matrix and Time > Series Indicator? > > I understand the MATA function is compiled and therefore local macro > substitution can't be done ... but was wondering if anyone else has an > elegant solution to reference different variables in MATA by changing a > component of the variablename (knowing the variable is defined in memory). > > Many Thanks, > Matthew > > Step #1: > ** > ** Import ALL MCP Matrix > ** > local Years = "1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 > 2007 2008 2009 2010" > clear all > local END = "end" > foreach year of local Years { > use [file_`year'.dta], clear // Load MCP Matrices into > Mata Memory // > drop ReporterISO3C > mata > Mcp_`year' = st_data(., .) > `END' > } > > Step#2: > ** MATA FUNCTION ** > > clear all > mata > void calcdiffvectors(real scalar StartYear, real scalar EndYear) { > for(year = StartYear; year < EndYear; year++) { > !!!!!!!!! local NextYear = `year' + 1 !!!!!!!!!!!!! > !!!!!!!!! Mcp_`year'_`NextYear' = Mcp_`year' :- Mcp_`NextYear' > !!!!!!!!!! > } > } > end > > Step #3: > mata: calcdiffvectors(1995, 2010) > // I can then retrieve the difference vectors using get mata etc. // > > -- Christophe Kolodziejczyk Research Fellow AKF, Anvendt KommunalForskning Danish Institute of Governmental Research Købmagergade 22 DK-1150 København K * * 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/

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