DAQmxCalculateReversePolyCoeff
int32 DAQmxCalculateReversePolyCoeff (float64 forwardCoeffs[], uInt32 numForwardCoeffsIn, float64 minValX, float64 maxValX, int32 numPointsToCompute, int32 reversePolyOrder, float64 reverseCoeffs[]);
Purpose
Computes a set of coefficients for a polynomial that approximates the inverse of the polynomial with the coefficients you specify with forwardCoeffs. The function generates a table of x versus y values over the range of x. The function then finds a polynomial fit, using the least squares method to compute a polynomial that computes an x given a y.
Parameters
| Input | ||
| Name | Type | Description |
|---|---|---|
| forwardCoeffs |
|
The array of the forward coefficients for the polynomial that computes y given a value of x. Each element of the array corresponds to a term of the equation. For example, if index 3 of the array is 9, the fourth term of the equation is 9x3. |
| numForwardCoeffsIn | uInt32 | The number of elements in forwardCoeff. |
| minValX | float64 | The minimum value of x for which you use the polynomial. This is the smallest value of x for which the function generates a y value in the table. |
| maxValX | float64 | The maximum value of x for which you use the polynomial. This is the largest value of x for which the function generates a y value in the table. |
| numPointsToCompute | int32 | The number of points in the table of x versus y values. The function spaces the values evenly between minValX and maxValX. |
| reversePolyOrder | int32 | The order of the reverse polynomial to compute. For example, an input of 3 indicates a 3rd order polynomial. An input of -1 indicates to compute a reverse polynomial of the same order as the forward polynomial. |
| Output | ||
| reverseCoeffs |
|
The array of the reverse coefficients of the polynomial. Each element of the array corresponds to a term of the equation. For example, if index 3 of the array is 9, the fourth term of the equation is 9y3. reverseCoeffs will be one greater than what you passed for reversePolyOrder. If you pass -1 for reversePolyOrder, the array must be the size of forwardCoeffs. Otherwise, the behavior is undefined. |
Return Value
| Name | Type | Description |
|---|---|---|
| status | int32 | The error code returned by the function in the event of an error or warning. A value of 0 indicates success. A positive value indicates a warning. A negative value indicates an error. |