Measure the change of data points from the line; Catch Dip

Question

How to measure this area in C ++?

(update: I sent the solution and code as an answer, rather than editing the question again)

The ideal line (dashed red) is a graph from the starting point, with the average growth increasing with each angle of measurement; I get it on average. I measured the test data in black. How can I quantify the area of ​​incidence in blue? The X axis is unified, so slopes and math are simplified.

I could determine the cutoff for such areas, and then mark this part for re-inspection or rejection. Rarely, there is another failure that appears closer to the right, but setting the cut-off value for the standard deviation usually leads to errors in these parts.

Update

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float sumOfDiffs=0.0;
for( int idx=0; idx<stop; idx++ ){
    float spread = deltas[idx] - line->AdcAvgRise;
    sumOfDiffs = sumOfDiffs + spread;
    ...
    testVal = 2*line->AdcAvgRise;
    if( sumOfDiffs > testVal || sumOfDiffs < -testVal ){
        flag = 'S';
    }
    ...
}

58 , sumOfDiffs AVG! , 120 sumOfDiffs -0.000057.

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Avg rise: 6.75    Std dev: 2.577
idx: delta  diff from avg   sumOfDiffs  Flag
 23:   5    -1.75           -14.05      S
 24:   6    -0.75           -14.80      S
 25:   7     0.25           -14.55      S
 26:   5    -1.75           -16.30      S
 27:   3    -3.75           -20.06      S
 28:   3    -3.75           -23.81      S
 29:   7     0.25           -23.56      S
 30:   4    -2.75           -26.31      S
 31:   2    -4.75           -31.06      S
 32:   8     1.25           -29.82      S
 33:   6    -0.75           -30.57      S
 34:   9     2.25           -28.32      S
 35:   8     1.25           -27.07      S
 36:   5    -1.75           -28.82      S
 37:  15     8.25           -20.58      S
 38:   7     0.25           -20.33      S
 39:   5    -1.75           -22.08      S
 40:   9     2.25           -19.83      S
 41:  10     3.25           -16.58      S
 42:   9     2.25           -14.34      S
 43:   3    -3.75           -18.09      S
 44:   6    -0.75           -18.84      S
 45:  11     4.25           -14.59      S
 47:   3    -3.75           -16.10      S
 48:   8     1.25           -14.85      S
 49:   8     1.25           -13.60      S
Final Sum of diffs: 0.000030
RunningStats analysis:
NumDataValues= 125
Mean= 6.752
StandardDeviation= 2.577
Skewness= 0.251
Kurtosis= -0.277

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Answer 2

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int dipdx=0;
//  inDipFlag also counts the length of this dip
int inDipFlag=0;
float dips[140] = { 0.0 };
for( int idx=0; idx<stop; idx++ ){
    const float diffFromAvg = deltas[idx] - line->AdcAvgRise;
    //  state machine to monitor dips
    const int _stop = stop-1;
    if( diffFromAvg < 0 && idx < _stop ) {
        //  check NEXT data point for negative diff & set dipFlag to put state in dip
        const float nextDiff = deltas[idx+1] - line->AdcAvgRise;
        if( nextDiff < 0 && inDipFlag == 0 )
            inDipFlag = 1;
        //  already IN a dip, and next diff is negative
        if( nextDiff < 0 && inDipFlag > 0 ) {
            inDipFlag++;
        }

        //  accumulate this dip
        dips[dipdx]+= diffFromAvg;

        //  next data point ends this dip and we advance dipdx to next dip
        if( inDipFlag > 0 && nextDiff > 0 ) {
            if( inDipFlag < dipCountLimit ){
                //  reset the accumulator, do not advance dipdx to next entry
                dips[dipdx]=0.0;
            } else {
                //  change this entry value from dip sum to its ratio
                dips[dipdx] = -dips[dipdx]/inDipFlag;
                //  advance dipdx to next entry
                dipdx++;
            }
            //  Next diff isn't negative, so the dip is done
            inDipFlag = 0;
        }
    }
}