The indexed sum

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The indexed sum is the sum of  a numerical object, named value to be summed obtained when a variable (called the index  variable) takes all the integer values between the start and end values of index specified.

The sum is calculated as follows :

Variable index is given all the integer values from mini value to maxi value. Each time, all the elements elements of the figure depending on  value to be summed and depending on variable index are re-calculated. The value to be summed is added to the sum and so on.


Let us have a simple example :

We have already defined a real function f , a variable N current value of which is 10.

We wish to calculate the sum of all f(k) for k in the range from 1 to N.

We will use a variable k with minimal value of 1, maximal  value of 100, step 1 and current value 2. We will notice that mini, maxi values and the step values of the variable are not used by the sum

Then we create a calculus named v (the value to be summed) that will contain the formula f(k).

Then we will use icon of the calculations expandable bar (third from the bottom).

Enter S as name for the sum.

Choose v as value to be summed.

Choose k for index variable.

Choose 1 for start index.

Choose N for end index.


To be noticed  : This sum is dynamic.Modifying  N value will modify the sum value.