/**
* 1d discrete fourier transform, note that this will throw an exception if the passed in input
* isn't a vector. See matlab's fft2 for more information
*
* @param inputC the input to transform
* @return the the discrete fourier transform of the passed in input
*/
public static ComplexNDArray complexDiscreteFourierTransform1d(ComplexNDArray inputC) {
if (inputC.shape().length != 1)
throw new IllegalArgumentException("Illegal input: Must be a vector");
double len = Math.max(inputC.rows, inputC.columns);
ComplexDouble c2 = new ComplexDouble(0, -2).muli(FastMath.PI).divi(len);
ComplexDoubleMatrix range = MatrixUtil.complexRangeVector(0, len);
ComplexDoubleMatrix matrix = exp(range.mmul(range.transpose().mul(c2)));
ComplexDoubleMatrix complexRet = matrix.mmul(inputC);
return ComplexNDArray.wrap(inputC, complexRet);
}
/**
* 1d discrete fourier transform, note that this will throw an exception if the passed in input
* isn't a vector. See matlab's fft2 for more information
*
* @param inputC the input to transform
* @return the the discrete fourier transform of the passed in input
*/
public static ComplexFloatMatrix complexDiscreteFourierTransform1d(ComplexFloatMatrix inputC) {
if (inputC.rows != 1 && inputC.columns != 1)
throw new IllegalArgumentException("Illegal input: Must be a vector");
float len = Math.max(inputC.rows, inputC.columns);
ComplexFloat c2 = new ComplexFloat(0, -2).muli((float) FastMath.PI).divi(len);
ComplexFloatMatrix range = MatrixUtil.complexRangeVector(0, len);
ComplexFloatMatrix matrix = exp(range.mmul(range.transpose().mul(c2)));
ComplexFloatMatrix complexRet =
inputC.isRowVector() ? matrix.mmul(inputC) : inputC.mmul(matrix);
return complexRet;
}
/**
* 1d inverse discrete fourier transform see matlab's fft2 for more examples. Note that this will
* throw an exception if the input isn't a vector
*
* @param inputC the input to transform
* @return the inverse fourier transform of the passed in input
*/
public static ComplexFloatMatrix complexInverseDisceteFourierTransform1d(
ComplexFloatMatrix inputC) {
if (inputC.rows != 1 && inputC.columns != 1)
throw new IllegalArgumentException("Illegal input: Must be a vector");
float len = MatrixUtil.length(inputC);
ComplexFloat c2 = new ComplexFloat(0, -2).muli((float) FastMath.PI).divi(len);
ComplexFloatMatrix range = MatrixUtil.complexRangeVector(0, (int) len);
ComplexFloatMatrix div2 = range.transpose().mul(c2);
ComplexFloatMatrix div3 = range.mmul(div2).negi();
ComplexFloatMatrix matrix = exp(div3).div(len);
ComplexFloatMatrix complexRet =
inputC.isRowVector() ? matrix.mmul(inputC) : inputC.mmul(matrix);
return complexRet;
}
