Scatter plots and lines
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I am wanting to add in a line like the graph below, but cannot seem to get the black line to stop going upwards. The gradient of the line is 4, please see my code and help!
clearvars;
close all;
clc;
% Extracted data
L = [0.2, 0.21, 0.22, 0.23, 0.24, 0.25]; % Length in µm
G = [0.002073593, 0.002034555, 0.00198774, 0.00194322, 0.00191650, 0.00188695]; % G in µm⁻¹
V = [33.4790, 35.0453, 35.5131, 35.7370, 36.2533, 36.3155]; % V in µm/s
% Plotting
figure;
hold on;
% Plot G vs V as a regular line plot
plot(V, G, 'o', 'LineWidth', 2, 'Color', 'b', 'MarkerFaceColor', 'b', 'DisplayName', 'Data');
% Add a black line with gradient = 4 starting from the origin
m = 4; % Gradient
V_line = linspace(0, max(V)+1, 100); % Start from 0
G_line = m * V_line;
plot(V_line, G_line, 'k-', 'LineWidth', 2, 'DisplayName', 'Gradient = 4 (from origin)');
% Formatting the plot
xlabel('Velocity V (µm/s)', 'FontSize', 30);
ylabel('Thermal Gradient G (µm⁻¹)', 'FontSize', 30);
title('G vs V for Varying Separation Distances', 'FontSize', 35);
legend('Location', 'northeast', 'FontSize', 20);
grid on;
xlim([min(0, min(V)-0.5), max(V)+0.5]);
ylim([min(0, min(G)-0.00001), max(G)+0.00001]);
3 个评论
The gradient of the line in the graphics (in [°C / s]) is approximately
(2.5e-3-1.4e-3)/(44-25)
Walter Roberson
2025-4-24
Your question does not indicate where you want the black line to stop ?
Cris LaPierre
2025-4-24
Your code does not recreate the image shown.
Note that you have defined the equation of the line to go from 0 to 37.3155 along X and 0 to 4*(36.3155 + 1), or 149.2620, along Y:
% Add a black line with gradient = 4 starting from the origin
m = 4; % Gradient
V_line = linspace(0, max(V)+1, 100); % Start from 0
G_line = m * V_line;
plot(V_line, G_line, 'k-', 'LineWidth', 2, 'DisplayName', 'Gradient = 4 (from origin)');
回答（1 个）
Hi @Harvey
Could you add a thick black line as indicated by the dotted lines? The dotted lines serve as a tracing task, helping you become familiar with forming lines, which is a crucial step in learning to plot in MATLAB.
clearvars;
close all;
clc;
% Extracted data
L = [0.2, 0.21, 0.22, 0.23, 0.24, 0.25]; % Length in µm
G = [0.002073593, 0.002034555, 0.00198774, 0.00194322, 0.00191650, 0.00188695]; % G in µm⁻¹
V = [33.4790, 35.0453, 35.5131, 35.7370, 36.2533, 36.3155]; % V in µm/s
% Plotting
figure;
hold on;
%% ------- Added or modified :: Start -------
lgd = legend('');
title(lgd, 'L (cm)')
% Plot G vs V as a regular line plot
plot(V(1), G(1), 'o', 'LineWidth', 2, 'Color', 'r', 'MarkerFaceColor', 'r', 'DisplayName', '20');
plot(V(2), G(2), 'o', 'LineWidth', 2, 'Color', 'y', 'MarkerFaceColor', 'y', 'DisplayName', '21');
plot(V(3), G(3), 'o', 'LineWidth', 2, 'Color', 'g', 'MarkerFaceColor', 'g', 'DisplayName', '22');
plot(V(4), G(4), 'o', 'LineWidth', 2, 'Color', 'c', 'MarkerFaceColor', 'c', 'DisplayName', '23');
plot(V(5), G(5), 'o', 'LineWidth', 2, 'Color', 'b', 'MarkerFaceColor', 'b', 'DisplayName', '24');
plot(V(6), G(6), 'o', 'LineWidth', 2, 'Color', 'm', 'MarkerFaceColor', 'm', 'DisplayName', '25');
xLine = [25 45.8];
yLine = [1.4e-3 2.5e-3];
line(xLine, yLine, 'Color', 'k', 'LineStyle', '--')
lgd.String(7) = '';
lgd.Location = 'northeast';
text(26.3, 2.3e-3, 'Stable', 'FontSize', 12)
text(45.3, 1.3e-3, 'Unstable', 'FontSize', 12)
xlim([25 50])
ylim([1e-3 2.5e-3])
%% ------- Added or modified :: End -------
% Add a black line with gradient = 4 starting from the origin
m = 4; % Gradient
V_line = linspace(0, max(V)+1, 100); % Start from 0
G_line = m * V_line;
% plot(V_line, G_line, 'k-', 'LineWidth', 2, 'DisplayName', 'Gradient = 4 (from origin)');
% Formatting the plot
xlabel('Velocity V (µm/s)');
ylabel('Thermal Gradient G (µm⁻¹)');
title('G vs V for Varying Separation Distances');
% legend('Location', 'northeast', 'FontSize', 20);
grid on;
% xlim([min(0, min(V)-0.5), max(V)+0.5]);
% ylim([min(0, min(G)-0.00001), max(G)+0.00001]);
2 个评论
Same code, just leveraging some of the capabilities of MATLAB to consolidate.
% Extracted data
L = [0.2, 0.21, 0.22, 0.23, 0.24, 0.25]; % Length in µm
G = [0.002073593, 0.002034555, 0.00198774, 0.00194322, 0.00191650, 0.00188695]; % G in µm⁻¹
V = [33.4790, 35.0453, 35.5131, 35.7370, 36.2533, 36.3155]; % V in µm/s
% Plotting
% Plot G vs V as a regular line plot
p=gscatter(V, G, L*100,'rygcbm');
hold on
plot([25 45.8], [1.4e-3 2.5e-3], 'k--')
hold off
% Formatting the plot
xlabel('Velocity V (µm/s)');
ylabel('Thermal Gradient G (µm⁻¹)');
title('G vs V for Varying Separation Distances');
lgd = legend(p,'Location', 'northeast');
title(lgd,"L (cm)")
grid on;
text(26.3, 2.3e-3, 'Stable', 'FontSize', 12)
text(45.3, 1.3e-3, 'Unstable', 'FontSize', 12)
xlim([25 50]);
ylim([1 2.5]*1e-3);
Sam Chak
2025-4-25
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