MATLAB: Need to remove repeated adjacent elements in an array

diff()repeat values removeunique

I need to turn

[1 1 1 1 2 2 2 6 6 6 6 2 2 2 2] into [1 2 6 2]

unique() gives [1 2 6], but I want to preserve the second value

any advice?

Best Answer

Taking advantage of ‘logical indexing’, it is relatively straightforward:

A = [1 1 1 1 2 2 2 6 6 6 6 2 2 2 2];
B = A(diff([0 A])~=0);

The code looks for changes in the differences (from the diff function) in ‘A’, then finds the elements in ‘A’ that correspond to those changes.

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MATLAB: How to fit a series of datapoints using 3 piecewise linear fit lines

Use this FEX

load data.mat % attached above
ydata(end) = []; % your xdata/ydata do not match in length ! 
slope0 = struct('p', 1, 'x', [min(xdata) max(xdata)], 'v', [0 0]);
% Download BSFK function here
% https://www.mathworks.com/matlabcentral/fileexchange/25872-free-knot-spline-approximation
pp = BSFK(xdata,ydata, 2, 3, [], struct('KnotRemoval', 'none', 'pntcon', slope0)); 
% Check
figure
xi = linspace(min(xdata),max(xdata));
yi = ppval(pp,xi)
plot(xdata,ydata,'b',xi,yi,'r');
for xb=pp.breaks
    xline(xb);
end
grid on

MATLAB: Matrix symbolic calculation doesn’t simplify expressions

try simplify - here is an example with your expression:

syms w
E = eye(3) * - (2^(1/2)*((2^(1/2)*w*1i)/2 - 2^(1/2)/8))/2 + (2^(1/2)*((2^(1/2)*w*1i)/2 + 2^(1/2)/8))/2
Simple_E = simplify(E)

gives:

E =
 
[ - (2^(1/2)*((2^(1/2)*w*1i)/2 - 2^(1/2)/8))/2 + (2^(1/2)*((2^(1/2)*w*1i)/2 + 2^(1/2)/8))/2,                                                (2^(1/2)*((2^(1/2)*w*1i)/2 + 2^(1/2)/8))/2,                                                (2^(1/2)*((2^(1/2)*w*1i)/2 + 2^(1/2)/8))/2]
[                                                (2^(1/2)*((2^(1/2)*w*1i)/2 + 2^(1/2)/8))/2, - (2^(1/2)*((2^(1/2)*w*1i)/2 - 2^(1/2)/8))/2 + (2^(1/2)*((2^(1/2)*w*1i)/2 + 2^(1/2)/8))/2,                                                (2^(1/2)*((2^(1/2)*w*1i)/2 + 2^(1/2)/8))/2]
[                                                (2^(1/2)*((2^(1/2)*w*1i)/2 + 2^(1/2)/8))/2,                                                (2^(1/2)*((2^(1/2)*w*1i)/2 + 2^(1/2)/8))/2, - (2^(1/2)*((2^(1/2)*w*1i)/2 - 2^(1/2)/8))/2 + (2^(1/2)*((2^(1/2)*w*1i)/2 + 2^(1/2)/8))/2]
 
 
Simple_E =
 
[            1/4, (w*1i)/2 + 1/8, (w*1i)/2 + 1/8]
[ (w*1i)/2 + 1/8,            1/4, (w*1i)/2 + 1/8]
[ (w*1i)/2 + 1/8, (w*1i)/2 + 1/8,            1/4]

Best Answer

Related Solutions

MATLAB: How to fit a series of datapoints using 3 piecewise linear fit lines

MATLAB: Matrix symbolic calculation doesn’t simplify expressions

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