I have a matlab plot(graph) x,y axis and i want to find the maximum from x axis. How to find that?

a= [1 2 13 20 10 20 12 1 13 14]
b= [1:10:100]
plot(a,b)

I want to find the maximum('a') from the plot and then take the corresponding point let say 'a3,b3' and store it some where else and remove it from the plot. then I want to subtract 'a3' from every point left in 'a' and plot the graph. and I need to do this again till it reaches an thresh hold point.

Answer 1

[Image Analyst]

Try this demo and see if it does what you want (plotting, finding, saving, and removing max, then subtracting max from what's left).

fontSize = 24;
a= [1 2 13 20 10 20 12 1 13 14];
b= [1:10:100];
storedMaxima = zeros(1, length(a));
loopCounter = 1; % For storing the maxima
hFig = figure;
while ~isempty(a)
  % Plot what we have.
  plot(b, a, 'b*-', 'MarkerSize', 19, 'LineWidth', 2);
  grid on;
  xlabel('b', 'FontSize', fontSize);
  ylabel('a', 'FontSize', fontSize);
  
  % Enlarge figure to full screen.
  set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
  
  % See if they want to quit now.
  if length(a) > 1
    promptMessage = sprintf('Do you want to Continue processing,\nor Quit?');
    titleBarCaption = 'Continue?';
    button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Quit', 'Continue');
    if strcmpi(button, 'Quit')
      break;
    end
  end
  
  % Find the max
  [maxValue, indexOfMax] = max(a);
  % Store the maxima
  storedMaxima(loopCounter) = maxValue;
  loopCounter = loopCounter + 1;
  % Remove the max
  a(indexOfMax) = [];
  b(indexOfMax) = [];
  % Subtract the max from a.
  a = a - maxValue;
end
% Print maxima to command window:
storedMaxima
uiwait(helpdlg('Done with demo.'));
close(hFig); % Close down figure.

[Sidhant Guliani]

 I have set of points from the measurement that i took and i wanna run clean algo.
                CLEAN ALGORITHM
1. plot power(P) Vs angle(q).
   P= [1 2 13 20 10 20 12 1 13 14]
   q= [1:10:100] 
2. find the Pmax and corresponding q let say qmax.
3. plot a triangular pattern with same no. of points as that in earlier plot , with one point of y axis= 1 and two adjacent ponts 0.5, rest 0 and able to circularly shift.
4. multiply it by Pmax.
5. move the pattern to the point such that peak matches. 
6. subtract pattern from plot.
7. note Pmax and crresponding angle.
8. remove this Pmax and corresponding angle.
9. repeat the process till it reaches Pthreashold.

[Image Analyst]

It looks like a different CLEAN algorithm than the famous one used in astronomy, but good luck with it. Let us know if you have any questions.

[Sidhant Guliani]

can you help me in writing the code for above mention 9 points.?