How to fit a line over a plot
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Angela Yang
el 7 de Abr. de 2023
Comentada: Mathieu NOE
el 13 de Abr. de 2023
Hi, I am trying to recreate this figure but I can't manage to figure out how to fit a smoothed line to summarise the frequencies. Also, the reference figure also includes the SEM which I'm struggling to recreate. My current plot is the grand averaged frequency spectra of simulated EEG data from 98 participants. Thanks!
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Mathieu NOE
el 11 de Abr. de 2023
hello
seems to me you want to plot the envelope of your spectra
there is a matlab function (Signal Processing Toolbox required) for that (envelope.m)
If you don't have the toolbox , here's an alternative (adapt to your own data) :
t = 0:0.01:10;
x = exp(-(t-5).^2/2).*sin(2*pi*5*t);
% obtain the envelope data
%--------------------------------------------
y = abs(hilbert(x)); % option 1 with hilbert
[up,down] = envelope2(t,x,'linear'); % option 2 with envelope2 (see below)
plot(t,x,t,y,'k',t,up,'m',t,down,'c')
legend('signal','hilbert','envelope2 / upper env','envelope2 / lower env');
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function [up,down] = envelope2(x,y,interpMethod)
%ENVELOPE gets the data of upper and down envelope of the known input (x,y).
%
% Input parameters:
% x the abscissa of the given data
% y the ordinate of the given data
% interpMethod the interpolation method
%
% Output parameters:
% up the upper envelope, which has the same length as x.
% down the down envelope, which has the same length as x.
%
% See also DIFF INTERP1
% Designed by: Lei Wang, <WangLeiBox@hotmail.com>, 11-Mar-2003.
% Last Revision: 21-Mar-2003.
% Dept. Mechanical & Aerospace Engineering, NC State University.
% $Revision: 1.1 $ $Date: 3/21/2003 10:33 AM $
if length(x) ~= length(y)
error('Two input data should have the same length.');
end
if (nargin < 2)|(nargin > 3),
error('Please see help for INPUT DATA.');
elseif (nargin == 2)
interpMethod = 'linear';
end
% Find the extreme maxim values
% and the corresponding indexes
%----------------------------------------------------
extrMaxIndex = find(diff(sign(diff(y)))==-2)+1;
extrMaxValue = y(extrMaxIndex);
% Find the extreme minim values
% and the corresponding indexes
%----------------------------------------------------
extrMinIndex = find(diff(sign(diff(y)))==+2)+1;
extrMinValue = y(extrMinIndex);
up = extrMaxValue;
up_x = x(extrMaxIndex);
down = extrMinValue;
down_x = x(extrMinIndex);
% Interpolation of the upper/down envelope data
%----------------------------------------------------
up = interp1(up_x,up,x,interpMethod);
down = interp1(down_x,down,x,interpMethod);
end
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