Plotting multiple functions from data stored in arrays.

I need to generate two values in a single plot with the condition that whenever data array (corresponding to the p_array) becomes negative ,those negative values aren't plotted.

Below is the function that i use to generate data

function data = negativity_data()
    arr = [];
    p_array = linspace(0, 0.5, 500);
    for p = p_array
        neg = Negativity(horodecki(4.3,p,0.9));
        arr = [arr; p neg];
    end
    data = arr;
end

Then i use data from this function into another function to plot

function f = negativity_plot()
    d = negativity_data();
    x = d(:,1);
    y = d(:,2);
    f = plot(x,y);
end

I similarly have another values

function data = realignment_data()
    arr = [];
    p_array = linspace(0, 0.5, 500);
    for p = p_array
        rea = 0.5*TraceNorm(Realignment(horodecki(4.3,p,0.9)))-0.5;
        arr = [arr; p rea];
    end
    data = arr;
end

%And the plot function
function f = realignment_plot()
    d = realignment_data();
    x = d(:,1);
    y = d(:,2);
    f = plot(x,y);
end

Answer 1

[Star Strider]

We do not have the arrays, however an approach using ‘logical indexing’ will probably work here —

x = linspace(0, 1, 5000).';
y = sin(2*pi*x) .* cos(2*pi*5*x);

figure
plot(x, y)
grid
title('Original')

Lv = y>0;                                                           % Logical Vector

figure
plot(x(Lv), y(Lv))
grid
title('Positive Values With Connecting Lines Plotted')

xnan = x;
ynan = y;
xnan(~Lv) = NaN;
ynan(~Lv) = NaN;

figure
plot(xnan, ynan)
grid
title('Positive Values Without Connecting Lines Plotted')

Since NaN values do not plot, the last figure has no lines connecting the positive segments.

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