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Invent random_normal() to provide normally-distributed random numbers.

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There is already a version of this in contrib/tablefunc, but it
seems sufficiently widely useful to justify having it in core.

Paul Ramsey

Discussion: https://postgr.es/m/CACowWR0DqHAvOKUCNxTrASFkWsDLqKMd6WiXvVvaWg4pV1BMnQ@mail.gmail.com
This commit is contained in:
Tom Lane
2023-01-09 12:44:00 -05:00
parent 2673ebf49a
commit 38d81760c4
10 changed files with 164 additions and 29 deletions
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26
doc/src/sgml/func.sgml
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@ -1815,6 +1815,28 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
<primary>random_normal</primary>
</indexterm>
<function>random_normal</function> (
<optional> <parameter>mean</parameter> <type>double precision</type>
<optional>, <parameter>stddev</parameter> <type>double precision</type> </optional></optional> )
<returnvalue>double precision</returnvalue>
</para>
<para>
Returns a random value from the normal distribution with the given
parameters; <parameter>mean</parameter> defaults to 0.0
and <parameter>stddev</parameter> defaults to 1.0
</para>
<para>
<literal>random_normal(0.0, 1.0)</literal>
<returnvalue>0.051285419</returnvalue>
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
@ -1824,7 +1846,8 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
<returnvalue>void</returnvalue>
</para>
<para>
Sets the seed for subsequent <literal>random()</literal> calls;
Sets the seed for subsequent <literal>random()</literal> and
<literal>random_normal()</literal> calls;
argument must be between -1.0 and 1.0, inclusive
</para>
<para>
@ -1848,6 +1871,7 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
Without any prior <function>setseed()</function> call in the same
session, the first <function>random()</function> call obtains a seed
from a platform-dependent source of random bits.
These remarks hold equally for <function>random_normal()</function>.
</para>
<para>