how to draw peaks in specific locations?

i need to draw peaks in specific coordinations how can i do it ?

[Image Analyst]

Read this: http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

Answer 1

[Star Strider]

Here is one way:

P = @(x,c,w) exp(-w*(x-c).^2);      % Function to calculate peaks
W = 2;                              % Width (constant here, can vary as a vector if you like)
C = 5:5:15;                         % Peak centers

x = linspace(0,20,250);             % Define ‘x’ vector

pks = zeros(size(x));               % Preallocate ‘pks’
for k1 = 1:length(C)                % Loop through ‘C’ (centers) vector
    pks = pks + P(x,C(k1),W);
end

figure(1)                           % Plot
plot(x,pks)
grid

produces:

[marc kahwaji]

no not like that i need to create peaks in specific coordinations similar to the function surf find attach the image to see the examples of peaks that i need to draw i need to draw them in specific coordinations

[Star Strider]

This does what you want:

P = @(x,y,c,w) exp(-((x-repmat(c(1),size(x,1),size(x,2))).^2 + (y-repmat(c(2),size(y,1),size(y,2))).^2)./w);    % Function to calculate peaks
W = 2;                              % Width (constant here, can vary as a vector if you like)
C = [[5 10 15 2 7 10 12 17]; [3 6 9 12 17 7 15 13]];    % Peak centers

x = linspace(0,20,150);             % Define ‘x’ vector

[X,Y] = meshgrid(x);

pks = zeros(size(X));               % Preallocate ‘pks’
for k1 = 1:size(C,2)                % Loop through ‘C’ (centers) vector
    pks = pks + P(X,Y,C(:,k1),W) * (-1)^k1;
end

figure(1)                           % Plot
meshc(X,Y,pks)
grid on

I alternated them to be positive or negative by multiplying them by (-1)^k1 simply to demonstrate that effect. Experiment with the centres and width to get the effect you want. If you want them different widths, you have to provide a vector of one width for each centre. The call to ‘P’ then becomes:

P(X,Y,C(:,k1),W(k1))

with everything else staying the same.

The code here produces:

[marc kahwaji]

thanks for your help :D

[Star Strider]

My pleasure!

[marc kahwaji]

i have one last question if i need to change the amplitude of each peak how can i do it?

[Star Strider]

You would need a separate vector for the amplitudes, just as for the widths.

The function changes to:

P = @(x,y,c,w,a) a .* exp(-((x-repmat(c(1),size(x,1),size(x,2))).^2 + (y-repmat(c(2),size(y,1),size(y,2))).^2)./w);    % Function to calculate peaks

with the additional ‘a’ argument being the amplitude, and the call to it changes to:

P(X,Y,C(:,k1),W(k1),A(k1))

There have to be as many elements in the W and A vectors as there are columns in the C matrix.

[marc kahwaji]

ok thank you very much

[Star Strider]

My pleasure!

The most sincere expression of gratitude here on MATLAB Answers is to Accept the Answer that most closely solves your problem.

[marc kahwaji]

i have modified a little bit the code to obtain colored circles

close all;
clear all;

P = @(x,y,c,w,a)  a.*exp(-((x-repmat(c(1),size(x,1),size(x,2))).^2 + (y-repmat(c(2),size(y,1),size(y,2))).^2)./w);
A=[6 8 10];
W = 1;                                                                                    % Width (constant here, can vary as a vector if you like)
C = [[18 15 5];[10 10 10]];    % Peak centers
x = linspace(0,20,150);             % Define ‘x’ vector

[X,Y] = meshgrid(x);
pks = zeros(size(X));               % Preallocate ‘pks’
 for k1 = 1:size(C,2)                % Loop through ‘C’ (centers) vector
     pks = pks + P(X,Y,C(:,k1),W,A(k1)) ;
 end

A=meshz(X,Y,pks);
view(2);

grid on;

colorbar

i obtained colored circles if i need to put an image as a background for those circles how can i do it ?

Thanks for your help !!

[Star Strider]

My pleasure!

I don’t believe it’s possible to overplot the contour plot you’ve created and an image. At least I can’t find it anywhere in the documentation for core MATLAB or the Image Processing Toolbox.

You might want to post the image part of your Question as a separate Question. Image Analyst will likely see it there. If he can’t do it, it can’t be done. That’s out of my area of expertise.

[marc kahwaji]

okey thanks for your help !!

[Star Strider]

I see you posted that Question and Image Analyst provided an appropriate Answer. Accepting Image Analyst’s Answer and mine here would be an appropriate response from you.

[marc kahwaji]

this is my serial data code

clear all; delete(instrfind); s = serial('COM6'); instrfind set(s, 'InputBufferSize', 256); set(s, 'FlowControl', 'none'); set(s, 'BaudRate', 9600); set(s, 'Parity', 'none'); set(s, 'Timeout',1);

disp(get(s,'Name')); prop(1)=(get(s,'BaudRate')); prop(2)=(get(s,'DataBits')); prop(3)=(get(s, 'StopBit')); prop(4)=(get(s, 'InputBufferSize'));

disp(['Port Setup Done!!',num2str(prop)]); fopen(s); instrfind

stopTime = '9/24 21:53'; time = now;

i=1; j=1;

while ~isequal(datestr(now,'mm/DD HH:MM'),stopTime)

 d(i,j)=fscanf(s,'%f')   %reading serial data and putting them in a matrix
 e=d(:,1)'               %values of the first sensor
 f=d(:,end)'             %values of the second sensor 
 subplot(1,2,1);
 plot(e)                 %plotting the values of the first sensor
 grid
 subplot(1,2,2);
 plot(f)                 %plotting the values of the second sensor
 grid

j=j+1; if j==3 % if the index of columns of the matrix is 3

     i=i+1;             %we go to a new line of the matrix we increment the index of lines
     j=1;               %and we put the index of columns to 1
end ;

drawnow end; fclose(s); delete(s);

clear all;

i have serial data coming from two sensors.I'm putting them in a matrix then splitting them in two matrix: e and f. e contains the values of the first sensor and f contains the values of the second sensor. i need to draw two circles, one for each sensor, and i need to color them according to the values in matrix e and f. how can i do it?