Stata Numeric Functions

Stata supports these numeric functions in the global scope.

Contents

  1. Stata Numeric Functions
    1. General Purpose
    2. Date and Time Functions
    3. Statistical Functions
    4. Max
    5. Mdy
    6. Mdyhms
    7. Min
    8. Mod
    9. Real
    10. Round
    11. RUniform
    12. Sign
    13. SqRt
    14. String
    15. StrOfReal
    16. Sum
    17. Trunc
    18. Y
    19. Yh
    20. Ym
    21. Yq
    22. Yw

General Purpose

Function Name

Meaning

Example

abs(n)

Absolute value function

ceil(n)

Round up to an integer

comb(n,k)

[[Statistics/Combinations|Combinatorial function

exp(n)

Exponential function: en

expm1(n)

High precision implementation of exp(n)-1

floor(n)

Round down to an integer

int(n)

Round towards 0 to an integer

-5 = int(-5.8)

invlogit(n)

Inverse logit function

ln(n)

Natural log function

logit(n)

Logit function

ln1m(n)

High precision implementation of ln(n-1)

ln1p(n)

High precision implementation of ln(n+1)

round(n,p)

Round to the nearest value for a given precision

Date and Time Functions

Function Name

Meaning

Output Format

Example

dhms(d,h,m,s)

Attach hour, minute, and second data to a date

%tc

dmy(d,m,y)

Calculate a date from a year, month, and day

%td

Cdhms(d,h,m,s)

Attach hour, minute, and second data to a date

%tC

hms(h,m,s)

Calculate a time from an hour, minute, and second

%tc

Chms(h,m,s)

Calculate a time from an hour, minute, and second

%tC

Note that %tc formats ignore leap seconds, while %tC formats do not.

Statistical Functions

Function Name

Meaning

Example

invnormal

Inverse cumulative standard normal distribution

1.959964 = invnormal(1-0.05/2)

normal

Cumulative standard normal distribution

.9750021 = normal(1.96)

Max

Mdy

Convert a month, day, and year into the number of days since the Stata epoch (01jan1960 00:00:00.000). 

generate long date = mdy(month, day, year)
format date %td

Mdyhms

Convert a day, month, year, hour, minute, and second into the number of milliseconds since the Stata epoch (01jan1960 00:00:00.000) ignoring leap seconds. 

generate double datetime = mdyhms(month, day, year, hour, minute, second)
format date %tc

See also Cmdyhms, which creates returns a number that should instead be formatted as %tC because it does not ignore leap seconds.

Min

Mod

Real

Round

RUniform

runiform(a,b) returns a random number between a and b. If no parameters are specified, the defaults of 0 and 1 are used.

Below is a demonstration for how an SRS sample can be drawn. 

set seed 123456
generate double r_sampled = runiform()
sort r_sampled
generate byte sampled = _n <= 100

The return value is a double; it will be within a + c(epsdouble) and b − c(epsdouble).

By default, runiform uses the 64-bit Mersenne Twister algorithm. Alternate algorithms are available; see set rng.

See also set seed for designing deterministic programs.

Sign

SqRt

String

Alias for strofreal.

StrOfReal

Sum

Trunc

Y

Convert a year into the number of years since the Stata epoch (01jan1960 00:00:00.000). 

generate int year = y(year)
format year %ty

Yh

Convert a year and half year into the number of half years since the Stata epoch (01jan1960 00:00:00.000). 

generate int halfyears = yh(year, halfyear)
format halfyears %th

Ym

Convert a year and month into the number of months since the Stata epoch (01jan1960 00:00:00.000). 

generate int months = y(year, month)
format months %tm

Yq

Convert a year and quarter into the number of years since the Stata epoch (01jan1960 00:00:00.000). 

generate int quarters = yq(year, quarter)
format quarters %tq

Yw

Convert a year and week into the number of weeks since the Stata epoch (01jan1960 00:00:00.000). 

generate int weeks = yw(year, week)
format weeks %tw

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