How to create different Plots for different functions while each function has been plotted using hold on

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Aditya Prasad 2022-9-6

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https://ww2.mathworks.cn/matlabcentral/answers/1796845-how-to-create-different-plots-for-different-functions-while-each-function-has-been-plotted-using-hol

编辑： Aditya Prasad 2022-9-6

I created a code to calculate entropy and enthalpy for different pressures (which forms my x axis) at different temperatures.

I want to plot isotherms for enthalpy and using hold on, multiple isotherms in the same plot.

But using "hold on" not only clubs the different isotherms for enthalpy together in one plot, but also clubs entropy isotherms into the same plot too. Due to the difference in order of magnitude between the two, the entropy lines are simply not visible. Scaling enthalpy down by 10^3 has helped in making both of them visible but I want them to be in seperate graphs or plots.

%enthalpy plot (KJ/mol Vs Bar)-
    hold on;
    for t = 1:nt %varying temperature to create isotherms
        for p = 1:np
            enth(1, p) = 0.001*enthalpy(T(1, t), P(1, p), [T_ref, P_ref, H_ref], [A B], [a b c], R);
        end
        plot1 = plot(P, enth); %one plot for particular value of temperature
    end
    hold off
%entropy plot (J/K Vs Bar)- 
    hold on
    for t = 1:nt
        for p = 1:np
            ent(1, p) = entropy(T(1, t), P(1, p), [T_ref, P_ref, S_ref], [A B], [a b c], R);
        end
        plot2 = plot(P, ent);
    end

the indivisual functions of entropy and enthalpy are trivial, the long list of arguments is basically temperature and pressure that i want to calculate the function in plus the refernce states and constants.

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Answer 1

dpb 2022-9-6

在 MATLAB Online 中打开

%enthalpy plot (KJ/mol Vs Bar)-
    hold on;
    for t = 1:nt %varying temperature to create isotherms
        for p = 1:np
            enth(1, p) = enthalpy(T(1, t), P(1, p), [T_ref, P_ref, H_ref], [A B], [a b c], R);
        end
        plot1 = plot(P, enth); %one plot for particular value of temperature
    end
    figure
%entropy plot (J/K Vs Bar)- 
    hold on
    for t = 1:nt
        for p = 1:np
            ent(1, p) = entropy(T(1, t), P(1, p), [T_ref, P_ref, S_ref], [A B], [a b c], R);
        end
        plot2 = plot(P, ent);
    end

What you missed is simply creating a new figure for the second plot.

Or you could use tiledlayout and have two subplots instead.

As a stylistic and computing note; if the two functions enth and entropy were vectorized, then you could simply call them with the T,P arrays and get back the arrays of results eliminating the looping at the outer level.

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dpb 2022-9-6

That's what I put in the code I posted in the Answer -- just insert the figure command and presto! a whole new figure window appears....

Aditya Prasad 2022-9-6

编辑：Aditya Prasad 2022-9-6

Oh i didn't see the change lol. Thanks a ton ! exactly what i had in mind, didn't know it would be this simple.

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Answer 2

Cris LaPierre 2022-9-6

在 MATLAB Online 中打开

Perhaps what you need is to create a plot with two y axes, one for entropy and the other for enthalpy? If so, use yyaxis.

x = linspace(0,10);

y = sin(3*x);

yyaxis left

plot(x,y)

z = sin(3*x).*exp(0.5*x);

yyaxis right

plot(x,z)

ylim([-150 150])

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Aditya Prasad 2022-9-6

this does solve the problem of scaling perhaps but as there are multiple isotherms corresponding to multiple temperatures, i'd much rather have them on different graphs all together

Cris LaPierre 2022-9-6

在 MATLAB Online 中打开

Then you need to create a new figure for each one before plotting. Use the figure command

x = linspace(0,10);

y = sin(3*x);

plot(x,y)

figure

z = sin(3*x).*exp(0.5*x);

plot(x,z)

ylim([-150 150])

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