How can i optimize the code and connect the functions?

Question

João Novais 2021-7-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/878433-how-can-i-optimize-the-code-and-connect-the-functions

评论： Star Strider 2021-7-16

采纳的回答： Star Strider

在 MATLAB Online 中打开

Hi everyone!

I've been dabbling with MatLab for the past three days and 've managed to write the following, working, code.

eta_l = xlsread('calculos.xlsx','Theoretical Predictions','S2');
eta_0 = xlsread('calculos.xlsx','Theoretical Predictions','S3');
l_c = xlsread('calculos.xlsx','Theoretical Predictions','P3');
sigma_f = xlsread('calculos.xlsx','Base Values','B3');
v_f = xlsread('calculos.xlsx','Burn','E23');
E_m = xlsread('calculos.xlsx','Base Values','D2');
E_f = xlsread('calculos.xlsx','Base Values','B2');
d = xlsread('calculos.xlsx','Base Values','B5');
%basically these functions y1 and y2 should be connected but i haven't been able to connect them
%plot of the Kelly-Tyson equation
x=linspace(-10,50);
idx = x < l_c;
y1=((eta_l.*eta_0.*((v_f.*sigma_f.*E_m)./(E_f.*d.*sqrt(3))).*x(idx))+((sigma_f.*E_m.*(1-v_f))./E_f));
y2=(eta_l.*eta_0.*(((-sigma_f.*v_f.*l_c)./2).*(1./x(~idx))+(sigma_f.*v_f)))+(((sigma_f.*E_m)./E_f).*(1-v_f));
plot(x(idx),y1,x(~idx),y2);
ylim([0 1000]);
grid on
hold on
%basically these next two bits are the same and i would like to not repeat
%them and get the same to points in the plot
%plot of the 95% of the max of the Kelly-Tyson equation
syms x
f=(eta_l.*eta_0.*(((-sigma_f.*v_f.*l_c)./2).*(1./x)+(sigma_f.*v_f)))+(((sigma_f.*E_m)./E_f).*(1-v_f));
maximus=limit(f,Inf);
eqn=f==0.95.*maximus;
S=solve(eqn,x);
plot(S,0.95.*maximus,'r*')
hold on
%plot of the 98% of the max of Kelly-Tyson equation
syms x
f1=(eta_l.*eta_0.*(((-sigma_f.*v_f.*l_c)./2).*(1./x)+(sigma_f.*v_f)))+(((sigma_f.*E_m)./E_f).*(1-v_f));
maximus1=limit(f1,Inf);
eqn1=f1==0.98.*maximus1;
S1=solve(eqn1,x);
plot(S1,0.98.*maximus1,'r*')
hold off

But... The last two bits are basically me writing them again and again. Is there a way where i can optimize the code so that i get a plot with the graphs of the functions connected - that is because they are connected in reality - and the points ploted but without having to write basically the same thing twice?

Thanks in advance!

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Answer 1

Star Strider 2021-7-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/878433-how-can-i-optimize-the-code-and-connect-the-functions#answer_746778

在 MATLAB Online 中打开

The syms call is not necessary.

Try something like this instead:

% syms x
f= @(x) (eta_l.*eta_0.*(((-sigma_f.*v_f.*l_c)./2).*(1./x)+(sigma_f.*v_f)))+(((sigma_f.*E_m)./E_f).*(1-v_f));
maximus = f(max(x));
eqn = @(x)f(x)*0.95.*maximus;
x0 = rand;
S=fsolve(eqn,x0);
plot(S,0.95.*maximus,'r*')
hold on
%plot of the 98% of the max of Kelly-Tyson equation
% syms x
f1= @(x) (eta_l.*eta_0.*(((-sigma_f.*v_f.*l_c)./2).*(1./x)+(sigma_f.*v_f)))+(((sigma_f.*E_m)./E_f).*(1-v_f));
maximus1=f1(max(x));
eqn1= @(x)f1(x)*0.98.*maximus1;
S1=fsolve(eqn1,x0);
plot(S1,0.98.*maximus1,'r*')
hold off

The functions each appear to be an inverse function of ‘x’, so will likely have only one root. (I cannot determine if the functions have a zero-crossing, so it is possible that there are no roots.) I am not certain what the limit call is doing, since the part of the function that contains the

term will go to 0 in the limit, leaving only the additive terms that are not a function of ‘x’.

.

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Star Strider 2021-7-15

在 MATLAB Online 中打开

This appears to produce the desired result (although I had to make a few changes to make this compatible with the online Run feature, that apparently does not like xlsread) —

filename = 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/685458/calculos.xlsx';

eta_l = readmatrix(filename,'Sheet','Theoretical Predictions','Range','S2:S2');

eta_0 = readmatrix(filename,'Sheet','Theoretical Predictions','Range','S3:S3');

l_c = readmatrix(filename,'Sheet','Theoretical Predictions','Range','P3:P3');

sigma_f = readmatrix(filename,'Sheet','Base Values','Range','B3:B3');

v_f = readmatrix(filename,'Sheet','Burn','Range','E23:E23');

E_m = readmatrix(filename,'Sheet','Base Values','Range','D2:D2');

E_f = readmatrix(filename,'Sheet','Base Values','Range','B2:B2');

d = readmatrix(filename,'Sheet','Base Values','Range','B5:B5');

%basically these functions y1 and y2 should be connected but i haven't been able to connect them

%plot of the Kelly-Tyson equation

x=linspace(-10,50);

x = linspace(-10,50);

y1 = @(x) ((eta_l.*eta_0.*((v_f.*sigma_f.*E_m)./(E_f.*d.*sqrt(3))).*x)+((sigma_f.*E_m.*(1-v_f))./E_f));

y2 = @(x) (eta_l.*eta_0.*(((-sigma_f.*v_f.*l_c)./2).*(1./x)+(sigma_f.*v_f)))+(((sigma_f.*E_m)./E_f).*(1-v_f));

y = y1(x).*(x < l_c) + y2(x).*(x >= l_c);

figure

plot(x, y)

grid

hold on

%basically these next two bits are the same and i would like to not repeat

%them and get the same to points in the plot

%plot of the 95% of the max of the Kelly-Tyson equation

% syms x

f= @(x) (eta_l.*eta_0.*(((-sigma_f.*v_f.*l_c)./2).*(1./x)+(sigma_f.*v_f)))+(((sigma_f.*E_m)./E_f).*(1-v_f));

maximus = f(1E+10);

% eqn = @(x)f(x)*0.95.*maximus;

x0 = rand;

S=fsolve(@(x)f(x)-0.95.*maximus,x0)

Equation solved. fsolve completed because the vector of function values is near zero as measured by the value of the function tolerance, and the problem appears regular as measured by the gradient.

S = 9.5928

plot(S,0.95.*maximus,'r*')

hold on

%plot of the 98% of the max of Kelly-Tyson equation

% syms x

f1= @(x) (eta_l.*eta_0.*(((-sigma_f.*v_f.*l_c)./2).*(1./x)+(sigma_f.*v_f)))+(((sigma_f.*E_m)./E_f).*(1-v_f));

maximus1=f1(1E+10);

% eqn1= @(x)f1(x)*0.98.*maximus1;

S1=fsolve(@(x)f1(x)-0.98.*maximus1,x0)

Equation solved. fsolve completed because the vector of function values is near zero as measured by the value of the function tolerance, and the problem appears regular as measured by the gradient.

S1 = 23.9819

plot(S1,0.98.*maximus1,'r*')

hold off

ylim([0 max(ylim)])

text(S, 0.95.*maximus, sprintf('\\uparrow\n(%.4f, %.4f)',S,0.95.*maximus), 'Horiz','left','Vert','top')

text(S1, 0.98.*maximus1, sprintf('(%.4f, %.4f)\n\\downarrow',S1,0.98.*maximus1), 'Horiz','right','Vert','bottom')

So my code works and produces a unified plot, and I corrected the ‘S’ and ‘S1’ calculations as well. (I will let you explore the changes to determine how they work.)

.

João Novais 2021-7-16