Reflect about y-axis after certain point in x.

I'm trying to simulative tidal wave and reflect the wave about the x-axis after 1 quarter of a lunar cycle.

What I want is to mirror about the x-axis what i currently have after x = 7.3826475.

This is my coding for the first quarter and what it looks importing data from an excel spreadsheet to give a damped sinusoidal shape.

data=xlsread('Tidal Sites.xlsx');
A=data(:,9);
B=data(:,10);
C=data(:,11);
D=data(:,12);
x1=linspace(0., 7.3826475, 10000);
y1=det(A(1))*((exp(1).^(det(-B(1)).*x1))).*sin((det(C(1)).*x1)+det(D(1)));
figure, plot(x1,y1), hold on

Answer 1

[Walter Roberson]

y2 = fliplr(y1);
x2 = x(end) + cumsum(mean(diff(x1)) * (1:length(x1)));

Note: the use of linspace for x does not actually give us enough information to construct as many more x values as already exist, only one fewer than that. linspace() is not equal interval, due to round-off considerations. The information that we can justify from the input values as a true reflection is

x2 = x(end) + cumsum(fliplr(diff(x)));

which will be one item shorter. The corresponding y is

y2 = fliplr(y1(1:end-1));

It depends on whether you want the last y to be duplicated or not. If the mirror is "at" the last value then the last should not be duplicated.