How can i code a Linreg for imported data (Elimination Capacity vs Loading Rate)

Hi guys - Im having some issue with perfoming via code on doing LinReg on the following imported data. I would like to calculate Linear regression on the variables named "Elimination Capacity" vs "Loading Rate". Can someone please give an coded solution - the goal is to plot in the code below. Please se code and its corresponding comments for guides.

%Defining and Importing data
filename = 'CATValuesoct22.xlsx';
data = readmatrix(filename);

% Assign the columns to variables
EliminationCapacity = data(:,1); %  elimination capacity is in the first column
LoadingRate = data(:,2); %  loading rate  is in the second column
RemovalEfficiency = data(:,3); %  removal efficiency is in the third column
EliminationCapacity_100 = data(:,2);

%Linreg of variables EliminationCapacity and LoadingRate 
%HOW CAN I CODE IT and use it in the code for plot below

%plot for oct
% Create a figure
figure
% Set the first y-axis
yyaxis left
plot(LoadingRate, RemovalEfficiency, '*','LineWidth', 2);
ylabel('Removal Efficiency [%]');

% Set the second y-axis
yyaxis right
plot(LoadingRate, EliminationCapacity,'.--','LineWidth', 2);
ylabel('Elimination Capacity [g/(m^3*h)]');
hold on
plot(LoadingRate, EliminationCapacity_100, 'g--', 'LineWidth', 2);

% Set x-axis
xlabel('Loading Rate [g/(m^3*h)]');
% Add a title
title('October');
% Add a legend
legend('Removal Efficiency', 'Elimination Capacity','100% Elimination Capacity');

Best Regards - Amil Ali

Answer 1

[Vijeta]

To calculate the linear regression between the variables "Elimination Capacity" and "Loading Rate" and plot the results, you can use the “polyfit” function in MATLAB. Here's how you can modify your code to include the linear regression calculation and the corresponding plot:

matlabCopy code :

% Defining and Importing data 
filename = 'CATValuesoct22.xlsx'; 
data = readmatrix(filename); 
 
% Assign the columns to variables 
EliminationCapacity = data(:,1); % elimination capacity is in the first column 
LoadingRate = data(:,2); % loading rate is in the second column 
RemovalEfficiency = data(:,3); % removal efficiency is in the third column 
EliminationCapacity_100 = data(:,2); 
 
% Perform linear regression 
coeffs = polyfit(LoadingRate, EliminationCapacity, 1); 
linear_fit = polyval(coeffs, LoadingRate); 
 
% Plot for oct 
% Create a figure 
figure 
 
% Set the first y-axis 
yyaxis left 
plot(LoadingRate, RemovalEfficiency, '*','LineWidth', 2); 
ylabel('Removal Efficiency [%]'); 
 
% Set the second y-axis 
yyaxis right 
plot(LoadingRate, EliminationCapacity,'.--','LineWidth', 2); 
hold on 
plot(LoadingRate, EliminationCapacity_100, 'g--', 'LineWidth', 2); 
plot(LoadingRate, linear_fit, 'r-', 'LineWidth', 2); % Plot the linear regression line 
 
% Set x-axis 
xlabel('Loading Rate [g/(m^3*h)]'); 
 
% Add a title 
title('October'); 
 
% Add a legend 
legend('Removal Efficiency', 'Elimination Capacity','100% Elimination Capacity', 'Linear Fit'); 
 
% Adjust the figure layout 
grid on;

In the above code, “polyfit” is used to calculate the coefficients of the linear regression line. The “polyval” function is then used to evaluate the linear fit at each point along the LoadingRate values. Finally, the linear fit is plotted on the figure using “plot” along with the other data.

Make sure you have the appropriate data file ('CATValuesoct22.xlsx') in the current working directory or provide the correct path to the file.

Polynomial curve fitting - MATLAB polyfit (mathworks.com)

Polynomial evaluation - MATLAB polyval (mathworks.com)