Findlevels Algorithm

#pragma rtGlobals=3     // Use modern global access method and strict wave access.

//-----------------------------------------------------------------------------------------
//                  LOOK FOR INDEX
//-----------------------------------------------------------------------------------------
//      This function act as the Igor's function "FindLevels"
//-----------------------------------------------------------------------------------------


Function/WAVE LookForIndex(dataWave,level, boxSize)
    Wave dataWave
    Variable level      // threshold to be crossed
    Variable boxSize    // box size for sliding average, should preferably be an odd number
       
    boxSize = ceil((boxSize-1)/2)   // take the half size of the box
       
    Variable length = numpnts(dataWave)
    Variable i, j
    Variable slidingAverage
    Variable lookForRisingEdge = 1
   
    Make/O/N=10000 indexWave // we assume that we have less than 10000 crossing level. If not, change this value.
   
    for(i = 0; i < length; i+=1)   
       
        slidingAverage =  mean(dataWave,i-boxSize,i+boxSize)    // comput the sliding average  
           
        if ( (slidingAverage > level) && (lookForRisingEdge == 1))  // look for rising edge
           
            indexWave[j] = i           
            lookForRisingEdge = 0          
            j=j+1
           
        elseif ( (slidingAverage) < level && (lookForRisingEdge == 0 )) // look for falling edge
                   
            indexWave[j] = i           
            lookForRisingEdge = 1          
            j=j+1              
        endif
           
    endfor
       
    Redimension /N=(j) indexWave   
   
    return indexWave // All "X" values at which the "level" was crossed
   
End