Cumulative standard deviation: Difference between revisions

This REXX version uses running sums.

<lang rexx>/*REXX pgm finds & displays the standard deviation of a given set of numbers.*/

parse arg # /*any optional arguments on the C.L. ? */

if #='' then # = 2 4 4 4 5 5 7 9 /*None specified? Then use the default*/

w=words(#); L=length(w); $=0; $$=0 /*# items; item width; couple of sums*/

/* [↓] process each number in the list*/

do j=1 for w; _=word(#,j); $=$+_; $$=$$+_**2

say ' item' right(j,L)":" right(_,4) ' average=' left($/j,12),

' standard deviation=' left(sqrt( $$/j - ($/j)**2 ), 15)

end /*j*/ /* [↑] prettify output with whitespace*/

exit /*stick a fork in it, we're all done. */

/*────────────────────────────────────────────────────────────────────────────*/

sqrt: procedure; parse arg x; if x=0 then return 0; d=digits(); numeric form

numeric digits 11; parse value 11 format(x,2,1,,0) 'E0' with m. g 'E' _ .

g=g*.5'E'_%2; p=d+d%4+2; do j=0 while p>9; m.j=p; p=p%2+1; end

do k=j+5 to 0 by -1; if m.k>11 then numeric digits m.k; g=.5*(g+x/g); end

numeric digits d; return g/1</lang>

'''output''' &nbsp; when using the default input of: &nbsp; <tt> 2 &nbsp; 4 &nbsp; 4 &nbsp; 4 &nbsp; 5 &nbsp; 5 &nbsp; 7 &nbsp; 9 </tt>