how plot two slopes for one curve

Hi,

I have one curve. I want to plot two slopes; the first slop is for points 1,2,3 and 4. The second slope is to plot the rest of the points. I attached a figure of this.

Answer 1

[Naga]

Hello Hisham,

It understand you want to plot two different slopes for different segments of your data. Based on the image you provided, here’s how you can achieve that:

1. Separate the points for the two slopes.
2. Use the polyfit function to find the slope for each segment.
3. Use the plot function to visualize the data points and the fitted lines.

Here’s a sample code:

% Define data points
x = 2000:500:7000;
y = -17:0.5:-12;

% Separate points for two slopes
x1 = x(1:4); y1 = y(1:4);
x2 = x(5:end); y2 = y(5:end);

% Calculate slopes
p1 = polyfit(x1, y1, 1);
p2 = polyfit(x2, y2, 1);

% Plot data points and fitted lines
figure;
scatter(x, y, 'filled'); hold on;
plot(x1, polyval(p1, x1), '-r', 'LineWidth', 2);
plot(x2, polyval(p2, x2), '-b', 'LineWidth', 2);

% Add labels and legend
xlabel('X-axis'); ylabel('Y-axis');
legend('Data points', 'First slope', 'Second slope');
title('Plot with Two Slopes');
hold off;

Refer the below documentation links to read more about the functions:

1. polyfit: https://www.mathworks.com/help/matlab/ref/polyfit.html
2. polyval: https://www.mathworks.com/help/matlab/ref/polyval.html