MATLAB: Count Relationships between two columns

countcountif

I'd like to count how many links a first column number is to a second column number, and so on. For example, how many times the number 1da first column has the number 1 in the second column?

Best Answer

maxdata = max(max(Yourdata(:,1:2)));
counts = accumarray(YourData(:,1:2), 1, [maxdata, maxdata]);

Now counts(J,K) is the number of times the number J appeared in the first column with K in the second column of the same row.

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MATLAB: Error from a relationship

Your model is the linear regression of the first 2000 points. To get the model predictions for the rest of the data, ‘plug in’ the values for your independent variable for the rest of your data in your model. The output of your model are the predictions for those values. To get the error, subtract your predictions from the dependent variable data for those same values of the independent variable.

To illustrate:

x = linspace(0,200);                        % Create Data
y1 = 0.5*x(1:50) + 0.1*randn(1,50) + 1.2;     % Create Data To Fit
y2 = 0.6*x(51:100) + 0.1*randn(1,50) + 1.5; % Create Data To Evaluate Error
b = polyfit(x(1:50), y1, 1);                % Parameter Estimates
yfit = polyval(b, x);                       % Predict Entire Data Set
model_error = yfit - [y1 y2];               % Calculate Error
figure(1)
plot(x, [y1 y2], 'xr')
hold on
plot(x, yfit, '-b')
hold off
grid
legend('Data', 'Model Fit', 'Location','SE')

MATLAB: How to count occurrences of a number in a column in relation to an other column occurrence

took some time but there a way

sum(A(:,2)==1 & A(:,3)==7)

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Related Solutions

MATLAB: Error from a relationship

MATLAB: How to count occurrences of a number in a column in relation to an other column occurrence

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