MATLAB: Interpolation of a scatter plot

Question

Hello ;I would be most grateful if someone could give me a helping hand. i have a scatter plot where the the third variable is velocity color coded for each pair of (x,y)I woud like to interpolate this plot to have more points.below is a figure of what i have and my code as well . thanks in advance.

the interpolated points are the red piont of the second figure is having just 9 pionts. i would like to apply that to the first figure which is what i have .

plotTypes  = {'mean_velocity','std_velocity','mean_pd',  'std_pd'};
for i = 1: length(plotTypes)
    figure
    plotType = plotTypes{i};
    %subplot(1,length(plotTypes), i);
     hold all ;
    legendLabels = cell(1,length(plotData));
    for j = 1:length(plotData)
        xPlot= plotData{j}.data(:, idx.x);
        yPlot= plotData{j}.data(:, idx.(plotTypes{i}));
        plot(xPlot,yPlot, '-o','color',k(j,:));
        legendLabels{j} = ['Y = ', num2str(plotData{j}.y)];
    end
    legend(legendLabels);
    title(plotTypes{i}, 'Interpreter', 'none');
    xlabel('x position')
    ylabel(plotTypes{i},  'Interpreter', 'none')
end
%% Generating the 3D color plot
% figure
for i = 1: length(plotTypes)
    figure
    legendLabels = cell(1,length(plotData));
    %     subplot(1,length(plotTypes), i);
    hold all
    for N=1:size(plotData,2)
       pz =150;
       plotData{1,N}.data();
       x=plotData{1,N}.data(:,1);
        y= plotData{1,N}.data(:,2);
        %if i ==3
        %  z= plotData{1,N}.data(:,(i+2));
        %end%         Z(:,N) =plotData{1,N}.data(:,(i+2));
        scatter(x,y,pz,plotData{1,N}.data(:,(i+2)),'filled')
        legendLabels{N} = ['Y = ', num2str(plotData{N}.y)];
      end
      %%Interpolation into a gridded data
      %F =scatteredInterpolant(x,y,Z);
      %[xq,yq]=meshgrid(linspace(20,230,100));
      %cq =F(xq,yq);
      %h=pcolor(xq,yq,cq)
      %legendLabels{N} = ['Y = ', num2str(plotData{N}.y)];
      legend(legendLabels);
      title(['3D plot of position against ',plotTypes{i}], 'Interpreter', 'none')
      xlabel('X(mm)')
      ylabel('Y(mm)')
      H = colorbar;
      ylabel(H, plotTypes{i});
end

Answer 1

Seems that scatteredInterpolant function would be better. Here is an example.

% Read data file
T = readtable('data.xlsx');
% Make interpolation function F = f(x,y)
F = scatteredInterpolant(T.xcoordinate,T.ycoordinate,T.mean_velocity);
% Make a grid points (20-by-20, for example)
[xmin,xmax] = bounds(T.xcoordinate);
[ymin,ymax] = bounds(T.ycoordinate);
[xGrid,yGrid] = meshgrid(linspace(xmin,xmax,20),linspace(ymin,ymax,20));
% Calculate interpolated value for each grid point
zGrid = F(xGrid,yGrid);
% Visualize the result
figure
scatter(xGrid(:),yGrid(:),[],zGrid(:),'filled')
colorbar