where is the error in my code?

2022 6 19
0 个回答
更新时间：2022 6 20
4 次查看（30 天）

0 个投票

Hi every one,
when I run the following code, I get a plot with unexpected two lines as circled by the red lines in the image attached! where is the error because we do not expect these lines to appear according to the physical equations?
V1 = @(r,w) -acosh(10*(w/(1600*r + 21))^(1/2))/20000000000
V2 = @(r,w) acosh(10*(w/(1600*r + 21))^(1/2))/20000000000
% Define function to be integrated
fun = @(x,r,w)0.0018./((w./((cosh(10^10.*x./0.5)).^2)-(r.*16+0.21)).^(1/2));
www = @(w,r)5.124-6.4*10^-6.*(exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2))).*log10((exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2)))))./(r.*(integral(@(x)fun(x,r,w),V1(r,w),V2(r,w)))))-(exp(-37.45.*r).*(70.31));
fimplicit(www,[0 5 0 0.075],'MeshDensity',500, 'LineWidth',1.5),grid

15 个评论
显示 13更早的评论 隐藏 13更早的评论

Torsten
Torsten 2022-6-19
I suggest you make a surface plot of www in the region of interest to see what happens.
help surf
Abdallah Qaswal
Abdallah Qaswal 2022-6-20
May you please help me plot the code with surf? because I tried using surf but I got an error, see here please:
V1 = @(r,w) -acosh(10*(w./(1600*r + 21))^(1/2))/20000000000
V2 = @(r,w) acosh(10*(w./(1600*r + 21))^(1/2))/20000000000
% Define function to be integrated
fun = @(x,r,w)0.0018./((w./((cosh(10^10.*x./0.5)).^2)-(r.*16+0.21)).^(1/2));
www = @(w,r)5.124-6.4*10^-6.*(exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2))).log10(exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2))))/(r.*(integral(@(x)fun(x,r,w),V1(r,w),V2(r,w)))))-(exp(-37.45.*r).*(70.31));
surf(www,[0 5 0 0.075],'MeshDensity',500, 'LineWidth',1.5),grid
Abdallah Qaswal
Abdallah Qaswal 2022-6-20
when I delete the log part (log10(exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2)))), the straight linear line on the left is removed, so I think the problem is in writing the common logarithm, right?
Also, the horizontal line was removed when I change the range of R values from [0 0.075] to [0.01 0.075] so I removed the 0 to avoid infinity.
But the line that is remained is the left linear line! any idea to remove it?
Torsten
Torsten 2022-6-20
Ran in:
Ran in:
The part of your formula
...^(1/2))).log10(...
is incorrect. There must be a * or / before the log10.
w = 0:0.05:5;
r = 0.001:0.001:0.075;
[W,R]=meshgrid(w,r);
www = @(w,r)5.124-6.4*10^-6.*(exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2))).log10(exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2))))/(r.*(integral(@(x)fun(x,r,w),V1(r,w),V2(r,w)))))-(exp(-37.45.*r).*(70.31));
surf(W,R,www(W,R))
Dot indexing is not supported for variables of this type.

Error in solution (line 4)
www = @(w,r)5.124-6.4*10^-6.*(exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2))).log10(exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2))))/(r.*(integral(@(x)fun(x,r,w),V1(r,w),V2(r,w)))))-(exp(-37.45.*r).*(70.31));
Abdallah Qaswal
Abdallah Qaswal 2022-6-20
编辑：Torsten 2022-6-20
Ran in:
Ran in:
I edited the code according to your suggestions but unfortunately, the code still in error:
w = 0:0.05:5;
r = 0.001:0.001:0.075;
[W,R]=meshgrid(w,r);
V1 = @(r,w) -acosh(10*(w./(1600*r + 21)).^(1/2))/20000000000;
V2 = @(r,w) acosh(10*(w./(1600*r + 21)).^(1/2))/20000000000;
% Define function to be integrated
fun = @(x,r,w)0.0018./((w./((cosh(10^10.*x./0.5)).^2)-(r.*16+0.21)).^(1/2));
www = @(w,r)5.124-6.4*10^-6.*(exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2))).*log10(exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2))))./(r.*(arrayfun(@(r,w)integral(@(x)fun(x,r,w),V1(r,w),V2(r,w)),R,W))))-(exp(-37.45.*r).*(70.31));
surf(W,R,www(W,R))
Warning: Inf or NaN value encountered.
Abdallah Qaswal
Abdallah Qaswal 2022-6-20
where is the problem?
Torsten
Torsten 2022-6-20
Ran in:
Ran in:
See the modified code from above.
You will have to check where and why the Inf and NaN values in the surface plotting appear.
I suggest you make a matrix M and inspect it:
w = 0:0.05:5;
r = 0.001:0.001:0.075;
[W,R]=meshgrid(w,r);
V1 = @(r,w) -acosh(10*(w./(1600*r + 21)).^(1/2))/20000000000;
V2 = @(r,w) acosh(10*(w./(1600*r + 21)).^(1/2))/20000000000;
% Define function to be integrated
fun = @(x,r,w)0.0018./((w./((cosh(10^10.*x./0.5)).^2)-(r.*16+0.21)).^(1/2));
www = @(w,r)5.124-6.4*10^-6.*(exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2))).*log10(exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2))))./(r.*(arrayfun(@(r,w)integral(@(x)fun(x,r,w),V1(r,w),V2(r,w)),R,W))))-(exp(-37.45.*r).*(70.31));
WWW = www(W,R);
Warning: Inf or NaN value encountered.
M(:,:,1) = W;
M(:,:,2) = R;
M(:,:,3) = WWW;
M(:,:,3)
ans = 75×101
1.0e+65 * -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 0.0000 0.0000 0.0000 0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 0.0000 0.0000 0.0000 0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000
Abdallah Qaswal
Abdallah Qaswal 2022-6-20
Thnak you! but this did not solve the original question because I would like to plot the relationship between R and W only without www, which is not a physical parameter in my case here!
As I told you, the issue is with the log part in the equation, any idea?
Abdallah Qaswal
Abdallah Qaswal 2022-6-20
Honestly, I do not understand the approach you suggested but what I noticed is that substituting the values on the undesired line on the left yields undefined values in the common logarithm like 0 or negative value, is there any function to exclude such undefined values?
Abdallah Qaswal
Abdallah Qaswal 2022-6-20
like just to take the real numbers
Torsten
Torsten 2022-6-20
编辑：Torsten 2022-6-20
Honestly, I do not understand the approach you suggested
MATLAB plots nonsense if www returns Inf or NaN.
So you will have to detect where this nonsense stems from in your definition of www.
Abdallah Qaswal
Abdallah Qaswal 2022-6-20
yes, the nonsens is (log of an exponential value), this one : log10(exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2)))) because once I remove it ( which does not affect the plot significantly), the plot was a desired one , do you have any idea how to address such log of an exponential function?
Torsten
Torsten 2022-6-20
log10(exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2)))) =
-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2)) / log(10)
Maybe this helps.
Abdallah Qaswal
Abdallah Qaswal 2022-6-20
Unfortunately, this also did NOT work, any other alternatives?
Abdallah Qaswal
Abdallah Qaswal 2022-6-20
I even put log 10 = 2.3, but still no desired results, here is the last modified code :
V1 = @(r,w) -acosh(10*(w/(1600*r + 21))^(1/2))/20000000000
V2 = @(r,w) acosh(10*(w/(1600*r + 21))^(1/2))/20000000000
% Define function to be integrated
fun = @(x,r,w)2.3*r.*0.0018./((w./((cosh(10^10.*x./0.5)).^2)-(r.*16+0.21)).^(1/2));
www = @(w,r)5.124+6.4*10^-6.*215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2)).*exp(-215.6*0.5*(w.^(1/2)-(r.*16+0.21).^(1/2)))./(integral(@(x)fun(x,r,w),V1(r,w),V2(r,w)))-(exp(-37.45.*r).*(70.31));
fimplicit(www,[0 5 0.001 0.075],'MeshDensity',500, 'LineWidth',1.5),grid

请先登录，再进行评论。

请先登录，再回答此问题。

回答（0 个）

类别

在 帮助中心 和 File Exchange 中查找有关 2-D and 3-D Plots 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by