MATLAB: Find max and min values, seperated by max or min

MATLABmaxmin

I have a large set of numbers and need to find two minimum values and two maximum values. However it shouldn't just be the two absolute max and min values they need to be seperated by a max or min value. So max,min,max,min.

Best Answer

Let A be your array.

[val1,idx1] = max(A) ;
A(idx1) = NaN ;
[val2,idx2] = max(A) ; 
if idx1 > idx2 
    [val3,idx3] = min(A(idx2:idx1)) ; 
else
    [val3,idx3] = min(A(idx1:idx2)) ; 
end
[val4,idx4] = min(A(idx2:end)) ;

Also read about findpeaks. Also you can sort array and get it.

Related Solutions

MATLAB: I am using Matlab to generate the plots for the examples and have managed to plot the function. For clarity sake I would like to place a red triangle at the global maximum and a blue square at the global minimum on the plot. Can you help me figure

t = linspace(0,2*pi) ;
y = sin(t) ;
plot(t,y) ;
hold on
%%maximum
[val1,idx1] = max(y) ;
scatter(t(idx1),y(idx1),'^r') ;
%%minimum 
[val0,idx0] = min(y) ;
scatter(t(idx0),y(idx0),'sb') ;

MATLAB: How to write such a loop

>> cell2mat(arrayfun(@(x,y) repmat(x,y,1),IDX1,segMem1,'uniform',0).')
ans =
   1
   1
   1
   2
   2
   1
   1
   3
   4
   4
>>

Since Matlab doesn't know about jagged arrays other than by cell array, you'll have to build the pieces and rearrange them into a cell array.

Oh, a spurious thought though I've never tried it; I suppose one could wrap a cellfun call around arrayfun, maybe to process the two cells as you've smushed them together above; otherwise a loop or the cell array.

ADDENDUM

OK, the looping construction works well enough...

>> for i=1:length(IDX)
     idx=IDX{i};
     seg=s{i};
     cell2mat(arrayfun(@(x,y) repmat(x,1,y),idx,seg,'uniform',0))
   end
ans =
   1     1     1     2     2     1     1     3     4     4
ans =
   3     3     1     2     2     1     1
>>

Left as row vectors for more compact display...

Best Answer

Related Solutions

MATLAB: I am using Matlab to generate the plots for the examples and have managed to plot the function. For clarity sake I would like to place a red triangle at the global maximum and a blue square at the global minimum on the plot. Can you help me figure

MATLAB: How to write such a loop

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