2.1.22.4.5 ocmath_smooth

1 Description
2 Syntax
3 Parameters
4 Return
5 Examples
6 Remark
7 See Also
8 Header to Include
9 Reference

Description

smoothing. have 3 methods: median filter, Savitzky-Golay smoothing and adjacent averaging smoothing.

Syntax

int ocmath_smooth( int nSize, const double * pY, double * pSmooth, int nLeftpts, int nMethod = SMOOTH_SG, int nBoundary = EDGEPAD_NONE, int nRightpts = -1, int nPolydeg = 2, int nDervOrder = 0, double dPercent = 50, bool bWeight = false, bool bAveraging = false )

Parameters

nSize: [input] vector size of both pY and pSmooth
pY: [input] pointer to Y vector data.
pSmooth: [output] pointer to smoothed data, or derivatives, depending on nDervOrder(only for Savitzky-Golay smoothing).
nLeftpts: [input] if do Savitzky-Golay smoothing,number of data points to the left to be used in filter convolution,; if do median filter, Number of surrounding points to left and right. Thus the number of points considered in each segment is (2*nPts + 1).; if do adjacent averaging smoothing, is the window's size.
nMethod: [input] smoothing method.; SMOOTH_ADJAVE adjacent averaging smoothing; SMOOTH_SG Savitzky-Golay smoothing; SMOOTH_MEDIAN_FILTER median filter
nBoundary: [input] data are padded on both ends. Possible values are; EDGEPAD_NONE no padding; EDGEPAD_REFLECT pad reflect, end points are repeated such that on the left, [-1] = [0], [-2] = [1], [-3] = [2] and etc; EDGEPAD_REPEAT pad with [0] values the left and with [nSize-1] on the right; EDGEPAD_EXTRAPOLATE linear extrapolation using nLeft points on the left and nRight points on the right; EDGEPAD_PERIODIC pad periodic, [-1] = [nSize -1], [-2] = [nSize - 2]
nRightpts: [input] for Savitzky-Golay smoothing. number of data points to the right to be used in filter convolution, default (-1) will assume nLeft.; Total number of points used in the polynomial fits are (nLeft + nRight + 1) and it must be odd, namely nLeft + nRight must be even.
nPolydeg: [input] for Savitzky-Golay smoothing.The polynomial order. Higher order will preserve sharper features. nPolyDeg must be less then (nLeft + nRight + 1).
nDervOrder: [input] for Savitzky-Golay smoothing. order of derivative desired (0 = smoothing). To generate a fourth derivative, a minimum quartic (order 4) smoothing must be used.; For a third derivative, a minimum cubic (order 3) smoothing is needed. Similarly, a second derivative requires a minimum quadratic (order 2) smoothing.
dPercent: [input] for median filter.The percent for computing median.
bWeight: [input] for adjacent averaging smoothing. weight smooth or not. default is not(FALSE)
bAveraging: [input] for median filter.If true, the function will average the most nearest neighbors if there is no match to the given percent.

Return

OE_NOERROR for success

Examples

EX1

//Assume in the current graph, curve's XY data is in the first data plot. This piece
//of code get the XY data of the curve from the first data plot and smooth on it. 
//The result is output in a new worksheet and the smoothing curve will plot in the 
//original data plot with color red.
void ocmath_smooth_ex1()
{
    GraphLayer gl = Project.ActiveLayer();
    if (!gl)
    {
        out_str("Active layer is not a graph.");
        return;
    }
 
    //get XY data from the first dataplot
    DataPlot dp = gl.DataPlots(0);                
    DataRange dr;
    vector vx, vy;
    if(dp.GetDataRange(dr))
    {
        DWORD dwPlotID;
        if(dr.GetData(DRR_GET_DEPENDENT | DRR_NO_FACTORS, 0, &dwPlotID, NULL, &vy, &vx) < 0)
        {
            printf("get data failed GetData");
            return;
        }
    }
    vector vSmooth;
    vSmooth.SetSize(vy.GetSize());
 
    //do Savitzky-Golay smoothing, Left=Right=7, quadratic
    int nRet = ocmath_smooth(vy.GetSize(), vy, vSmooth, 3,SMOOTH_SG, EDGEPAD_NONE, 3, 2);
 
    //new a worksheet to put the result
    Worksheet wks;
    wks.Create("Smooth");
    wks.SetSize(-1, 2);
    wks.SetColDesignations("XY");
    
    DataRange drOut;
    drOut.Add("X", wks, 0, 0, -1, 0);
    drOut.Add("Y", wks, 0, 1, -1, 1);
    drOut.SetData(&vSmooth, &vx);
    
    //plot the curve after smoothing
    int nPlot = gl.AddPlot(drOut, IDM_PLOT_LINE);
    dp = gl.DataPlots(nPlot);
    dp.SetColor(1);
}