Storing values calculated in a 'for' loop in a matrix / vector

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Tobias 2013-3-13

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I would very much appreciate some help storing values in a matrix. I am trying to do a growth curve (See: http://kellymom.com/images/growth/growthcharts.gif). For that reason I have to do quantile equations for a set of data (age and height). Currently, I've made a 'for' loop, which does calculate the value as intended, however it only stores the last result. How do I make it store the data as a matrix like:

Quantile 25 %

Age Height

6 123
7 129
8 135

and so forth.

Thank you very much!

Note: male.data consists of two columns. First column is age and second is height of two thousand male participants. The file: age.height.mat is my data.

[EDITED, Jan, contents of the M-file from dropbox:]

%%Assignment 1 - Growth curves for men and women
clear all ;
clc ;
load age.height.mat
% Sorting the data to be plotted
male.data = sortrows(male.data) ;
plot(male.data(:,1),male.data(:,2),'r+')
male.growth = zeros(1, 73);
t = zeros(1, 73); 
    for k = 6:78
      male.growth(k-5) = male.data(male.data(:,1) == k, 2);
      t(k-5) = quantile(male.growth(k-5), 0.5);
    end
% Note that t sometimes returns 'not a number', when a specific age is not
% present. That won't be a problem in my final script, as I am not allowed
% to publish all my data for copyright reasons.

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Tobias 2013-3-14

在 MATLAB Online 中打开

Anybody who can help me with fixing the dimension problem I am currently having?

"In an assignment A(I) = B, the number of elements in B and I must be the same."

male.growth(k-5) = male.data(male.data(:,1) == k, 2);

Tobias 2013-3-15

I would just like to add that I have solved my problem! So thank you for inspirational input

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Answer 1

Jan 2013-3-13

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/67005-storing-values-calculated-in-a-for-loop-in-a-matrix-vector#answer_78453

编辑：Jan 2013-3-13

在 MATLAB Online 中打开

Please do not start your code with the cruel killer. There is no benefit in removing all loaded functions from the memory by clear all. If you have a good reason to clear all variables, use clear variables or even better use a function, because it has its own workspace.

For storing the results in a vector:

male.growth = zeros(1, 73);  % Pre-allocate!!! Optional but recommended
t = zeros(1, 73); 
for k = 6:78  % Avoid using "i" as a variable
  male.growth(k-5) = male.data(male.data(:,1) == k, 2); % Without FIND
  t(k-5) = quantile(male.growth(k-5), 0.5);
end

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Tobias 2013-3-13

编辑：Tobias 2013-3-13

在 MATLAB Online 中打开

After having debugged and writing the code you suggested, I got the following:

K>> size(a)
ans =
     104     1

Which, as far as I understand, should correspond correctly with the 104 boys at the age of 6 included in my data. Even though the dimension of male.growth is 1 x 73 after the code:

male.growth = zeros(1, 73);

Isn't it supposed to automaticly change the dimensions of male.growth to the dimensions of the result in:

male.growth(k-5) = male.data(male.data(:,1) == k, 2);