bar with mean, std and significance star

Hi! How can I represent a bar graph of mean values and standard deviations with the star of significance level of a t-test upon the bars? I tried with 'barweb' but it doesn't work on my matlab version and also it does not display any significance stars. Thank you in advance! Gianluca

Answer 1

[Samayochita]

Hey Gianluca,

A bar graph can be created with error bars and significance stars in MATLAB using basic plotting functions like “bar”, “errorbar”, and “text” for the stars.

Here is how it could be achieved:

1. Compute Means and Standard Deviations.

means = [mean(data1), mean(data2)]; 
stds = [std(data1), std(data2)]; 

2. Plot bars for mean values. Adds error bars for standard deviations.

figure; 
b = bar(means, 'FaceColor', [0.2 0.6 0.5]); 
hold on; 
errorbar(1:2, means, stds, '.k', 'LineWidth', 1.5); 

3. Perform t-test to get p-values.

[h, p] = ttest2(data1, data2); 

4. Add Significance Stars (*, **, ***, or 'n.s.') using “text” and “plot” based on p-values.

if p < 0.001 
    stars = '***'; 
elseif p < 0.01 
    stars = '**'; 
elseif p < 0.05 
    stars = '*'; 
else 
    stars = 'n.s.'; 
end 
% Add stars above the bars 
maxY = max(means + stds) + 0.2; 
text(1.5, maxY, stars, 'HorizontalAlignment', 'center', 'FontSize', 14); 

For more information on the MATLAB functions used above, please refer to the following documentation links:

https://www.mathworks.com/help/matlab/ref/bar.html

https://www.mathworks.com/help/matlab/ref/errorbar.html

https://www.mathworks.com/help/matlab/ref/text.html