Category Archives: Stata

Stata commands to test equality of mean and median

UCLA IDRE has posted an article (link) that may provide a bit more explanation. UCLA IDRE is a great resource for learning statistical analysis. A big thank you to them.

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Handy Stata command to display combined Pearson and Spearman correlation matrix

Oftentimes we would like to display Pearson correlations below the diagonal and Spearman correlations above the diagonal. Two built-in commands, pwcorr and spearman, can do the job. However, we have to manually combine Stata output tables when producing the correlation table … Continue reading

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Stata command to convert string GVKEY to numerical GVKEY or vice versa

The default type of GVEKY in Compustat is string. Sometimes, we need it to be a numerical type in Stata (e.g., when we want to use the super handy command tsset). The command to convert string GVKEY to numerical GVEKY … Continue reading

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Stata command to calculate the area under ROC curve

If we want to evaluate the predictive ability of a logit or probit model, Kim and Skinner (2012, JAE, Measuring securities litigation risk) suggest that A better way of comparing the predictive ability of different models is to use the Receiver … Continue reading

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Stata commands to calculate skewness

Suppose we are going to calculate the skewness of 12 monthly returns. The 12 returns may be stored in a row (Figure 1) or in a column (Figure 2). This post discusses how to calculate the skewness in these two … Continue reading

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Commonly used Stata commands to deal with potential outliers

In accounting archival research, we often take it for granted that we must do something to deal with potential outliers before we run a regression. The commonly used methods are: truncate, winsorize, studentized residuals, and Cook’s distance. I discuss in … Continue reading

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Sample code for “outreg” command in Stata

outreg is very powerful and time-saving command in Stata. The following code generates a ready-for-use results table:

Please change x1, x2, x3 and x4 to variables that you want to report.

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A loop of cross-sectional regressions for calculating abnormal accruals in Stata

I write a loop of cross-sectional regressions for calculating abnormal accruals. This program can be easily modified and replaced with Jones, modified Jones, or Dechow and Dichev model. I add detailed comments in the program to help you prepare the input … Continue reading

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Rolling-window computation in SAS and Stata

SASers often find proc expand plus transformout very useful for rolling-window (or moving-window) computation. Stataers may wonder if there is a counter party in Stata. The answer is “yes”. The command in Stata is rolling. See the manual below: http://www.stata.com/manuals13/tsrolling.pdf The … Continue reading

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Regression with a large dummy-variable set (e.g., firm and year fixed effects) in Stata

I run a regression in Stata with a Compustat dataset that contains fyear and gvkey. I want to add firm and year fixed effects, so I type the following command: regress DV IV i.fyear i.gvkey But Stata returns the error … Continue reading

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