Summation

A summation expression has the form

     sum [<var> = <start> : <end>] <expression>

var

is treated as an integer variable that takes on successive integral values from $<$

start

end

. For each of these, the current value of $<$

expression $>$

is added to a running total whose final value becomes the value of the summation expression. Examples:

     print sum [i=1:10] i
         55.
     # Equivalent to plot 'data' using 1:($2+$3+$4+$5+$6+...)
     plot 'data' using 1 : (sum [col=2:MAXCOL] column(col))

It is not necessary that $<$

expression $>$

contain the variable $<$

var

. Although $<$

start

and

end

can be specified as variables or expressions, their value cannot be changed dynamically as a side-effect of carrying out the summation. If $<$

end

is less than $<$

start

then the value of the summation is zero.