MATLAB: If… then… else

if statement

Hello,

I have the following problem:

Assume a dataset [3000,1]
We construct a variable ‘signal’, which will have the same size of our dataset. ‘signal’ will be either 1 or -1, based on the evolution of our dataset.
At the starting point (1, 1), ‘signal’ will have the value 1. We keep this value until the dataset moves x % below its highest value during the time that ‘signal’ was equal to 1. From that moment on, the variable ‘signal’ will have the value -1.
We keep this value until the dataset moves x % above its lowest value during the time that signal was equal to -1. From that moment on, the variable ‘signal’ will have the value 1 again.
And so on, and so on…
A short example may make my problem more clear:

x = 10%

dataset / signal
97 / 1
100 / 1
93 / 1
89 / -1 / dataset moves x % below its highest value (100) during the '1' signal
86 / -1
80 / -1
93 / 1 / dataset moves x % above its lowest value (80) during the '-1' signal
94 / 1
95 / 1
92 / 1
80 -1 / dataset moves x % below its highest value (95) during the '1' signal
… …

Can anybody help me with this issue?

Thanks

Pieter

Best Answer

Try this solution:

A = [97 100 93 89 86 80 93 94 95 92 80];
% Preallocate
Out  = ones(size(A));
% First element is momentarily the maximum
maxA = A(1);
% Positive sequence
pos  = true;
% Tolerance of 10%
x    = .1;
% Start from the second element (since the first is considered the max)
for ii = 2:numel(A)
    % 1
    if pos
        % If new maximum
        if A(ii) > maxA
            maxA = A(ii);
        % If threshold is broken downwards
        elseif A(ii)/maxA-1 < -x
            minA    = A(ii);
            Out(ii) = -1;
            pos     = false;
        end
    % -1    
    else
        Out(ii) = -1;
        % If new minimum
        if A(ii) < minA
            minA = A(ii);
        % If threshold is broken upwards
        elseif A(ii)/minA-1 > x
            maxA    = A(ii);
            Out(ii) = 1;
            pos     = true;
        end
    end
end

Related Solutions

MATLAB: Grouping the pixel having same values

I =[83   81   81   84   85   84   82   82   84   81   83   83   81   81
83   81   81   83   83   82   80   81   83   80   82   83   81   79
81   79   83   84   84   84   81   81   82   80   81   81   79   79
79   80   82   86   85   84   83   83   85   85   81   81   79   79
79   81   84   85   85   83   83   83   84   83   81   83   81   81
84   83   84   85   85   83   84   80   81   81   81   82   82   83
83   84   86   85   85   83   84   80   79   80   82   82   81   83 ];
d = unique(I);
out = [];
for jj = 1:numel(d)
    r = bwconncomp(I == d(jj),4);
    out = [out;[repmat({d(jj)},r.NumObjects,1) r.PixelIdxList']];
end

or

d = unique(I);
out = [];
for jj = 1:numel(d)
    s=regionprops(bwconncomp(I == d(jj),4),'PixelList');
    out = [out;[repmat({d(jj)},numel(s),1) {s.PixelList}']];
end
[ii,ii] = sortrows(cell2mat(cellfun(@(x)x(1,:),out(:,2),'un',0)),[2 1]);
out = out(ii,:);

MATLAB: I have a problem

It is asked for "signed integer". Then uint32 is not an option, because it is unsigned.

x = 'NONE';   % requires quotes

The operator is missing in:

elseif maxA<= ((2^32)-1)   maxA > ((2^16)-1) ;
                        ^^

In addition this does not restrict the minA part.

You do not have to exclude e.g. the int8 range, if it was excluded already:

if maxA<=((2^7)-1) && minA>=-(2^7);
   x = 'int8';
elseif maxA<=((2^15)-1) && maxA>((2^7)-1) && minA>=-(2^15) && minA< -(2^7);
    x='int16';

Easier:

if maxA <= 2^7 - 1 && minA >= -2^7
   x = 'int8';
elseif maxA <= 2^15 - 1 && minA >= -2^15
   x = 'int16';

I'd prefer a loop:

TypeList = {'int8', 'uint8', 'int16', 'uint16', ...
            'int32', 'uint32', 'int64', 'uint64'};
x = 'NONE';
for k = 1:numel(TypeList)
  if isequal(double(A), double(cast(A, TypeList{k})))
    x = TypeList{k};
    break;
  end
end

Or:

minA = min(A(:));
maxA = max(A(:));
x    = 'NONE';
for aType = {'int8', 'int16', 'int32', 'int64'}
  aType = TypeList{k}
  if minA >= intmin(aType) && maxA <= intmax(aType)
     x = aType;
     break;
  end
end

Or

minA = min(A(:));
maxA = max(A(:));
x = 'NONE';
for k = [8,16,32,64]
  if minA >= -2^(k-1) && maxA <= 2^(k-1)
     x = sprintf('int%d', k);
     break;
  end
end

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