# Topographic plot Most of the beginners of EEG analysis field is looking for this visualization. Generally, the topographic plot shows the energy variation over the electrodes placed on the head. You can see a sample image of this visualization. Even if the plot is not that much elegant you can get an idea of the collected data. Topographic plot of 14 channel dataset

The Matlab code has been added below. Following code is created for 14 channel Emotiv EPOC+ headset electrode placement. But this code understandable and you can customize it for your own use. “xc” and “yc” contain coordinates of the electrodes. You have to edit those value according to your data. You can change the interpolation function to ‘linear’, ‘nearest’, ‘natural’, ‘cubic’, and ‘v4’ in line 30. Best function is ‘natural’ for this visualization.

 123456789101112131415161718192021222324252627282930313233343536373839404142 function topoplot(data) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % % Author: Isuru Jayarathne % % % % Input: 14xn matrix % % Output: Figure of the topographic plot % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Define electrodes placement according to the Emotiv Epoc+ headset xc = [2.5; 1.5; 3; 2; 1; 2; 3; 5; 6; 7; 6; 5; 6.5; 5.5]; yc = [7; 5.7; 5.8; 5; 4; 2; 1; 1; 2; 4; 5; 5.8; 6; 7]; lbls = {'AF3','F7','F3','FC5','T7','P7','O1','O2','P8','T8','FC6','F4','F8','AF4'}; trlen = []; % Calculating power of each electrode for i=1:14 ftr = (data(i,:)); ftr = fft(ftr); pow = ftr.*conj(ftr); tpow = sum(pow); trlen = vertcat(trlen,tpow); end xi=linspace(min(xc),max(xc),30); yi=linspace(min(yc),max(yc),30); [XI YI]=meshgrid(xi,yi); ZI = griddata(xc,yc,trlen,XI,YI,'natural'); figure; contourf(XI,YI,ZI,20); hold on; scatter(xc,yc,'b','filled'); text(xc+0.1,yc+0.1,lbls); % Turn off the plot labels and axis set(gca,'Visible','off'); colormap(jet); hold off; end

If you want to generate topographic plot for .edf file, please refer Github code.

#### References

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