# MagicPlot Manual

Plotting and nonlinear fitting software

### Sidebar

set_column_formula

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## Set Column Formula

Use Table → Set Column Formula menu item to open column formula dialog window.

See formula syntax.

## Row Index

Variable `i` contains the current row index.

## Rows Evaluation Order

Rows are always evaluated one after another from the first to the last in the specified range. Accordingly the row number `i` is incremented on each step.

##### Example

You can use this behaviour to calculate factorial: set `1` in the first row of column `A` and after that set formula `cell(A, i-1) * i` and rows interval from `2` to `100`. Note that formula is to be set for rows beginning from the second, and not from the first. You will get the factorial of row number (`i`).

## Using Table Data

There are two functions to obtain current table cell values in formula:

• `col(A)` – returns the value of cell in column 'A' in the current (i-th) row. Equivalent to `cell(A, i)`.
• `cell(A, 3)` – returns the value in column `A` and row `3`.

You can use either upper-case letters (`A…Z`, e.g. `col(B)`) or numbers (`1, 2, 3,..`, e.g. `col(1)`) in columns numeration in arguments of `col` and `cell` functions.

##### Example
• `col(A) + 15 + cell(B, i+1)`

## What is "Not-a-Number returned at row #" Warning?

Some mathematical functions can be defined only on a certain interval. For example, square root (`sqrt(x)`) is not defined for negative numbers (all calculations in MagicPlot are made in real numbers, not complex). Hence if the argument of `sqrt` is negative, a Not-a-Number (NaN) is returned. If a NaN value occurs in some part of formula, the result of calculation will also be a NaN, and corresponding table cells will be empty.

The calculations are not terminated if NaN value occurs in some row(s).

In some cases you may want to check if a `NaN` values occurs in calculations. MagicPlot shows the warning “Not-a-Number returned at row #”. This row number is the first row in which `NaN` value was returned. MagicPlot also highlights the function or operator which first produces NaN value.