How can I use various colors to fill the area under a normal distribution curve?

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Hi, I obtained a probability distribution for my data using the following syntax:
h = histfit(data);
and then:
pd = fitdist(data,'Normal');
I want to create a graph similar to Figure 1 using the mean and standard deviation values obtained from the histogram and fitted distribution.
In advance, I would like to express my gratitude for your assistance.
Figure 1:

Accepted Answer

Star Strider
Star Strider on 28 Nov 2023
Sure!
Try this —
x = linspace(1.5, 5, 250);
mu = 3.3;
s = 0.6;
y = normpdf(x, mu, s);
figure
plot(x, y)
hold on
Lv1 = (x>=mu) & (x<mu+s);
patch([x(Lv1) flip(x(Lv1))], [zeros(size(y(Lv1))) flip(y(Lv1))], 'g', 'EdgeColor','none')
Lv2 = (x>=mu+s) & (x<mu+2*s);
patch([x(Lv2) flip(x(Lv2))], [zeros(size(y(Lv2))) flip(y(Lv2))], 'y', 'EdgeColor','none')
Lv3 = (x>=mu+2*s) & (x<mu+3*s);
patch([x(Lv3) flip(x(Lv3))], [zeros(size(y(Lv3))) flip(y(Lv3))], 'r', 'EdgeColor','none')
hold off
If you want the text annotations as well, I can supply those, and the vertical lines, too.
.
  6 Comments
Navid
Navid on 28 Nov 2023
Thank you for your assistance. The second option was correctly implemented in my version. Thank you again.

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More Answers (2)

Angelo Yeo
Angelo Yeo on 28 Nov 2023
f = @(x, mu, sd) 1/(sd*sqrt(2*pi)) * exp(-1/2*((x-mu)/sd).^2);
x = linspace(1.5, 5, 1000);
mu = 3.25; sd = 0.5;
figure;
hold on;
x_zone1 = linspace(mu, mu+sd, 300);
x_zone2 = linspace(mu+sd, mu+2*sd, 300);
x_zone3 = linspace(mu+2*sd, mu+3*sd, 300);
area(x_zone1, f(x_zone1, mu, sd), 'FaceColor', 'g')
area(x_zone2, f(x_zone2, mu, sd), 'FaceColor', 'y')
area(x_zone3, f(x_zone3, mu, sd), 'FaceColor', 'r')
plot(x, f(x, mu, sd), 'color','k', 'linewidth', 2);

Chunru
Chunru on 28 Nov 2023
Edited: Chunru on 28 Nov 2023
data = randn(8192, 1);
h = histfit(data);
pd = fitdist(data,'Normal')
pd =
NormalDistribution Normal distribution mu = -0.00241653 [-0.0240676, 0.0192345] sigma = 0.999681 [0.984606, 1.01523]
figure;
x = linspace(-4*pd.sigma, 4*pd.sigma, 1001);
p = pdf(pd, x);
figure;
plot(x, p);
hold on
facecolor =["g", "y", "r"]
facecolor = 1×3 string array
"g" "y" "r"
for i=1:3
idx = (x >= (i-1)*pd.sigma) & (x < i*pd.sigma);
area(x(idx), p(idx), FaceColor=facecolor(i))
end
  3 Comments
Chunru
Chunru on 28 Nov 2023
It seems that you are using older version of matlab. Use the following name-value syntax for older version matlab.
area(x(idx), p(idx), 'FaceColor', facecolor(i))
Navid
Navid on 28 Nov 2023
Dear Chunru
I wanted to express my gratitude for the assistance you provided. I successfully modified your code and achieved my desired outcome thanks to your guidance. I appreciate your help.
mu = pd.mu; sd = pd.sigma;
x = linspace(mu-4*pd.sigma,mu+4*pd.sigma,1001);
p = pdf(pd,x);
figure;
plot(x,p);
hold on
facecolor=['g','y','r'];
for i=1:3
idx = (x>= mu+(i-1)*pd.sigma)&(x<mu+i*pd.sigma);
area(x(idx), p(idx), 'FaceColor', facecolor(i))
end

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