Author Archives: Kai Chen

SAS macro to count the number of analysts following a firm

This macro is used to count the number of analysts who followed a specific firm. Although this is a commonly used measure in literature, prior studies often give a vague description on what they do. The question is—what does “analysts … Continue reading

Posted in SAS | 2 Comments

Stata command to lowercase all variable names or the values of all string variables

Stata is a case-sensitive application, which can sometimes cause trouble. Therefore, we might want to convert all variable names or the values of all string variables to lowercase before further data processing. This post gives a quick method to do … Continue reading

Posted in Stata | 2 Comments

Stata command to order tabulation result with only top values shown

tabulate varname command is handy in Stata, but sometimes it returns a too long result, if varname contains too many unique values. The third-party command, groups, will solve the problem by showing top values only. Please use ssc install groups … Continue reading

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Empower “and” and “or” in IF statement in Stata

Stata is a little bit awkward when using and and or in if statement, compared to SAS. For example: In SAS, we can write if 2001 <= fyear <= 2010. But in Stata, we usually write: if fyear >= 2001 … Continue reading

Posted in Stata | 1 Comment

Display mean and median test results in Stata

Sometimes we may want to produce the following table to compare the mean and median of two groups: First of all, please refer to this post to see Stata commands to test equality of mean and median. However, it is … Continue reading

Posted in Stata | 22 Comments

Stata command to do Heckman two steps

We often see Heckman’s two steps in accounting literature. But how to do it in Stata? The two steps refer to the following two regressions: Outcome equation: y = X × b1 + u1 Selection equation: Dummy = Z × … Continue reading

Posted in Stata | 8 Comments

The calculation of average credit rating using ratings from three rating agencies

I was doing something in Finance and wanted to calculate the average rounded credit rating. Basically, I need to translate textual grades (e.g., AAA, Baa) to a numerical value. I found a clue in the following paper: Becker, B., and … Continue reading

Posted in Data | 1 Comment

Stata command to test equality of mean and median

Please read this post for how to display the results in a ready-for-use format. 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 … Continue reading

Posted in Stata | 3 Comments

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

Posted in Stata | 1 Comment

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

Posted in Stata | 1 Comment