I want a draw a line parallel to x axis in the existing graph while plotting itself

%Noisy data

ND=importdata('Noisydata.txt');

x3=ND(:,1);

y3=ND(:,2);

subplot(3,2,6);

plot(x3,y3)

title('Noisy Data')

Now I want to draw a line while this graph gets plotted as shown in the figure attached.

Answer 1

[Star Strider]

Try something like this —

x = 1:20;
y = randn(size(x));

xi = linspace(min(x), max(x), numel(x)*10);
yi = interp1(x, y, xi);
Lv = yi > 0;
zv = zeros(size(xi));

figure
plot(x, y)
hold on
patch([xi flip(xi)], [zv flip(yi.*Lv)], 'k', 'FaceAlpha',0.75)
hold off
grid

Experiment with the ‘Noisydata.txt’ signal.

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