Cumulative standard deviation: Difference between revisions

<lang rexx>/*REXX program to find the standard deviation of a given set of numbers.*/

parse arg # /*let the user specify numbers. */

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

w=words(#); s=0; ss=0 /*define: #items, a couple sums. */

do j=1 for w; _=word(#,j); s=s+_; ss=ss+_*_

say ' item' right(j,length(w))":" right(_,4),

' average=' left(s/j,12),

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

end /*j*/

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

/*──────────────────────────────────SQRT subroutine─────────────────────*/

sqrt: procedure;parse arg x; if x=0 then return 0; d=digits(); numeric digits 11; g=.sqrtGuess()

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

.sqrtGuess: numeric form; m.=11; p=d+d%4+2

parse value format(x,2,1,,0) 'E0' with g 'E' _ .; return g*.5'E'_%2</lang>

'''output''' using the default input

<pre style="overflow:scroll">

item 1: 2 average= 2 standard deviation= 0

item 2: 4 average= 3 standard deviation= 1

item 3: 4 average= 3.33333333 standard deviation= 0.942809047

item 4: 4 average= 3.5 standard deviation= 0.866025404

item 5: 5 average= 3.8 standard deviation= 0.979795897

item 6: 5 average= 4 standard deviation= 1

item 7: 7 average= 4.42857143 standard deviation= 1.39970843

item 8: 9 average= 5 standard deviation= 2

</pre>