Calculate the intersection of two waves
Posted September 24th, 2007 by aclight
The function below can be used to calculate the intersection of 2 one-dimensional integer waves, such as would be returned by the Extract operation using the /INDX flag. The intersection is stored in the resultWave parameter to the function. This wave must exist but will be redimensioned by the function as appropriate.
Example:
Make/O/N=5 wave1, wave2, wave3
wave1= {1, 2, 3, 4, 5}
wave2 = {3, 4, 5, 6, 7}
CalculateWaveIntersection(wave1, wave2, wave3)
print wave3
wave3[0]= {3,4,5}
Suggestions for improvements to this function are welcome.
//** // Calculates the intersection of two 1D integer waves. You might use this to determine // common indices in two destWaves created by the Extract/INDX operation. // // @param wave1 // First 1D integer wave. // @param wave2 // Second 1D integer wave. // @param resultWave // A wave where the result will be stored. This wave will be overwritten if it already contains // any data. The function will change the this to an integer wave if it is not already. //* Function CalculateWaveIntersection(wave1, wave2, resultWave) WAVE wave1 WAVE wave2 WAVE resultWave Variable wave1Rows = DimSize(wave1, 0) Variable wave2Rows = DimSize(wave2, 0) Variable longRows, shortRows if (wave1Rows > wave2Rows) Duplicate/O wave1, longWave WAVE shortWave = wave2 longRows = wave1Rows shortRows = wave2Rows else Duplicate/O wave2, longWave WAVE shortWave = wave1 longRows = wave2Rows shortRows = wave1Rows endif // Sort values in longWave Sort longWave, longWave Redimension/I/N=(0) resultWave Variable n, numOutRows, longWaveRow For (n=0; n<shortRows; n+=1) longWaveRow = BinarySearch(longWave, shortWave[n]) if ((longWaveRow) >= 0 && longWave[longWaveRow] == shortWave[n]) Redimension/N=(numOutRows + 1) resultWave resultWave[numOutRows] = shortWave[n] numOutRows += 1 endif EndFor KillWaves/Z longWave End