Differences between revisions 2 and 11 (spanning 9 versions)

Stata Numeric Functions

Stata supports these numeric functions in the global scope.

Contents

Stata Numeric Functions

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

CategoryRicottone

-  ⇤ ← Revision 2 as of 2022-03-16 15:42:29 → 
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+   ← Revision 11 as of 2025-03-04 19:55:57 → ⇥
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  Editor: DominicRicottone
  Comment: Partial rewrite
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+Stata supports these '''numeric functions''' in the global scope.
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-== Random Number Functions ==

=== Runiform ===
+== 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: ''e^n^''                  || ||
||`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 [[Statistics/Logit|logit function]]     || ||
||`ln(n)`            ||Natural log function                            || ||
||`logit(n)`         ||[[Statistics/Logit|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 ==
-Line 14:
+Line 128:
+Below is a demonstration for how an [[SurveySamples#Sampling_Methods|SRS sample]] can be drawn.
-Line 22:
+Line 138:
-The return value is a [[Stata/Types|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`'''.



=== Set Rng ===

To use an alternate random number generation algorithm, set the rng value to something other than `default`.

{{{
set rng default
}}}

Possible values include...

 * `mt64` (64-bit Mersenne Twister)
 * `mt64s` (stream algorithm based on the 64-bit Mersenne Twister)
 * `kiss32` (32-bit keep it simple stupid)

In Stata 14, the default flipped from `kiss32` to `mt64`.



=== Set Seed ===

To make random number generation reproducible, set a seed value.

{{{
set seed 42
}}}

A seed value must be an integer, non-negative, and no greater than 2^31^ − 1.
+The return value is a [[Stata/DataTypes|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 [[Stata/Set#Rng|set rng]].

See also [[Stata/Set#Seed|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
}}}

Diff for "Stata/NumericFunctions"