Taking mean of only specific values in column vector.

Hi , i have a column vector with 60 rows and 1 column as shown below. I want to take mean of only the values i.e 0.13 Can anybody suggest me how can i do that in MATLAB

[0.13
0.26
0.39
0.52
0.65
0.13
0.26
0.39
0.52
0.13
0.26
0.39
0.13
0.26
0.13
0.13
0.26
0.39
0.52
0.65
0.13
0.26
0.39
0.52
0.13
0.26
0.39
0.13
0.26
0.13
0.13
0.26
0.39
0.52
0.65
0.13
0.26
0.39
0.52
0.13
0.26
0.39
0.13
0.26
0.13
0.13
0.26
0.39
0.52
0.65
0.13
0.26
0.39
0.52
0.13
0.26
0.39
0.13
0.26
0.13]

Thank you

[Torsten]

The mean of the 0.13 values is 0.13. What are you exactly asking for ?

[Ahmad Bilal]

I want to take mean of all 0.13 values in my column vector .

[Torsten]

You really mean

mean(X(X==0.13))

??

[Image Analyst]

Try this:

theMean = 0.13;

otherwise take a look at ismembertol().

[Ahmad Bilal]

Sorry . Let me again ask the question in an another way. I have an excel with 2 column vectors x and y. Now x has different values such as 0.13,0.26,0.39 and so on. Now, I want to take mean in such a way that for every x=0.13 in column x there is corresponding value of y.

I want to take mean of values of y vector that correspondsto only x=0.13. PLease see an attached excel file.I hope this clears my point now.

[Torsten]

mean(y(x==0.13))

or

mean(y(ismembertol(x,0.13)))

Best wishes

Torsten.

[madhan ravi]

Deleted answer because Torsten is responding from the beginning:).

[Ahmad Bilal]

I have tried to do this but it shows : ans = NaN.

[madhan ravi]

Show us how you are loading the file.

[madhan ravi]

Contain the values as such values = [x y]

[Ahmad Bilal]

This is my code as follows :

dataset = xlsread('Test Excel file Mean and std.xlsx');
x = dataset(:,1);
y = dataset(:,2);

    scatter(x,y,'*');
  a = mean(y(x==0.13));

     hold on
     plot(a,y,'r+');
     grid on

[Image Analyst]

Torsten, please put your answer down below in the official Answer section, rather than as a comment up here where people ask for clarification. that way you can get credit (reputation points) for it. ?

[madhan ravi]

Exactly my thoughts @sir Image Analyst

[Ahmad Bilal]

Can you help me in this regard?

[madhan ravi]

Did you the contain the values?

[Ahmad Bilal]

I have made an excel sheet for theses values as I uploaded above.

[madhan ravi]

Add this line values = [x y] Before mean command

[Image Analyst]

Ahmad, I know. And I gave you a complete turnkey solution below. Did you try/see it?

[Ahmad Bilal]

I have tried it. It works perfectly fine . Now I want to display this point in my plot as i mentioned below. can you help me in this regard

Answer 1

[Image Analyst]

Try this:

fileName = 'Test Excel file Mean and std.xlsx';
data = xlsread(fileName)
rows = ismembertol(data(:, 1), 0.13, 0.001) % Rows where column 1 = 0.13
column2 = data(:, 2);
theMean = mean(column2(rows))

[Ahmad Bilal]

No my code looks like as follows :

dataset = xlsread('Test Excel file Mean and std.xlsx');

    x = dataset(:, 1);
    y = dataset(:, 2);
    scatter(x,y,'*');
    grid on
    a = ismembertol(dataset(:, 1), 0.13, 0.001); % Rows where column 1 
     = 0.13

      theMean = mean(y(a));

Now actually i want to display this mean valuei.e the mean in my scatter plot which corresponds to x=0.13. How can I do that ?

[Ahmad Bilal]

Like for every 0.13 in axis there is a stream of points in y axis. So i want to plot mean of y streams at x =0.13

[Ahmad Bilal]

Can anybody help me in that how can i display mean values at x= 0.13 in the above plot.

[Image Analyst]

Try this:

hold on;
plot(0.13, theMean, 'r*', 'LineWidth', 2, 'MarkerSize', 15);

[Ahmad Bilal]

Thank you for suggestion. It works perfectly fine

[Ahmad Bilal]

Now I want to calculate standard deviation for values corresponding to x=0.13 Actually i want to plot error bar which shows the error of points with respect to mean value that I have already calculated. I know how to plot error bars but i am confused how to use standard deviation as errorbars. Can anybody help me in this regard ???

[Image Analyst]

theMean = std(column2(rows))

[Ahmad Bilal]

I get this point but i am still confused how to use this std deviation as error bars. I know the syntax of error bars.

Actually My current figure looks as follows:I have already calculated mean shown as red squares.

Now I want to use standard deviation as error bars that will show my error of each blue points with respect to mean i.e red squares.

Can u suggest how can i display this kind of picture ? Thanks

[Image Analyst]

Use boxplot().

[Ahmad Bilal]

can you help me here with code snippet based on above mentioned variable in code uptil now I have the folllowing code as follows :

dataset = xlsread('Test Excel file Mean and std.xlsx');

   x = dataset(:, 1);
   y = dataset(:, 2);
   scatter(x,y,'*b');
   grid on
   a = ismembertol(dataset(:, 1), 0.13, 0.001);    % Rows where column 
    1 = 0.13
   b = ismembertol(dataset(:, 1), 0.26, 0.001);    % Rows where column 
   1 = 0.26
   c = ismembertol(dataset(:, 1), 0.39, 0.001);    % Rows where column 
   1 = 0.39
   d = ismembertol(dataset(:, 1), 0.52, 0.001);    % Rows where column 
   1 = 0.52
   e = ismembertol(dataset(:, 1), 0.65, 0.001);    % Rows where column 
   1 = 0.65

   values = [x y];
   theMean1 = mean(y(a));

   theMean2 = mean(y(b));
   theMean3 = mean(y(c));
   theMean4 = mean(y(d));
   theMean5 = mean(y(e));

   hold all;
   plot(0.13, theMean1, 'rs','MarkerFaceColor','r','MarkerSize',10);
   plot(0.26, theMean2, 'rs','MarkerFaceColor','r','MarkerSize',10);
   plot(0.39, theMean3, 'rs','MarkerFaceColor','r','MarkerSize',10);
   plot(0.52, theMean4, 'rs','MarkerFaceColor','r','MarkerSize',10);
   plot(0.65, theMean5, 'rs','MarkerFaceColor','r','MarkerSize',10);
% Here I want to use error bar command or box plot command to display error from mean values to each blue points for each corresponding x =0.13  0.26 and so on

   xlabel('distance d b/w mic pairs[cm]');
   ylabel('\phi_r_a_t_i_o');
   title('Relationship between \phi ratio and distance between Mic 
  Pairs for Array 3');