Last Modified: January 12, 2018

Determines a zero of a function in a given interval using the Ridders' method. You define the function with a formula.

Formula that defines the function.

Entering Valid Variables

This node accepts variables that use the following format rule: variables must start with a letter or an underscore followed by any number of alphanumeric characters or underscores.

Start value of the interval.

**Default: **0

End value of the interval.

**Default: **1

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an **error in** input and an **error out** output so that the node can respond to and communicate errors that occur while code is running. The value of **error in** specifies whether an error occurred before the node runs. Most nodes respond to values of **error in** in a standard, predictable way.

**Default: **No error

Conditions that terminate the process of finding zeros.

This node terminates the process of finding zeros if this node reaches the **accuracy** threshold or passes the **maximum iterations** threshold.

Maximum deviation of the calculated solution from the actual solution when determining the zeros.

**Default: **1E-08

Maximum number of iterations that the node runs to determine the zeros.

**Default: **200

Determined value of the independent variable where the function evaluates to zero.

This value is an approximation of the actual value of the variable where the function evaluates to zero.

Function value at **zero**. The value is expected to be nearly zero.

Number of evaluations of the formula to determine the zeros.

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

**error in** input and an **error out** output so that the node can respond to and communicate errors that occur while code is running. The value of **error in** specifies whether an error occurred before the node runs. Most nodes respond to values of **error in** in a standard, predictable way.

Given the function *f*(*x*) with *f*(*a*) * *f*(*b*) < 0, Ridders' method calculates *c*_{new} using the following equation:

${c}_{\mathrm{new}}=c+(c-a)\frac{\mathrm{sign}\left(f\left(a\right)-f(b))f\right(c)}{\sqrt{{f\left(c\right)}^{2}-f\left(a\right)f(b)}}$

where

*c*_{new}is the new guess to be used in the new iteration*a*and*b*are given values of the variable that satisfy*f*(*a*) **f*(*b*) < 0- $c=\frac{a+b}{2}$

The values **start**, *c*_{new}, and **end** are the base for the new iteration, depending on which of the following inequalities is true:

*f*(**start**) * *f*(*c*_{new}) < 0

*f*(*c*_{new}) * *f*(**end**) < 0

The algorithm stops if |*a* - *b*| < **accuracy**.

To determine the zero of *x*^{2} + sin(*x*) - 1 in the interval (0, 1), enter the following values on the panel.

formula |
x^2+sin(x)-1 |

start |
0 |

end |
1 |

The following table lists the outputs of this node.

zero |
0.636733 |

f(zero) |
3.20245E-09 |

function calls |
8 |

**Where This Node Can Run: **

Desktop OS: Windows

FPGA: Not supported

Web Server: Not supported in VIs that run in a web application