Applying 'if' condition within location-dependent thermal Properties

Question

Grzegorz 2021-7-21

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/882978-applying-if-condition-within-location-dependent-thermal-properties

回答： Jan 2021-7-21

Hallo!

I am using an external function ro_ult to calculate location-dependent mass density for a single-cell, 3-D thermal PDE analysis:

function ro_ult = ro_ult(location, state)
ro_s = 1300;
ro_d = 1800;
    if location.y <=0
        ro_ult = @(location,state) ro_d-(ro_d-ro_s)*exp(location.y/0.06);
    else
        ro_ult=1.6;
    end
end

Any attempt to use the function produces a following error:

Not enough input arguments.

Error in <a href="matlab:matlab.internal.language.introspective.errorDocCallback('ro_ult', 'ro_ult.m', 4)" style="font-weight:bold">ro_ult</a> (<a href="matlab: opentoline('ro_ult.m',4,0)">line 4</a>)

if location.y <=0

Error in <a href="matlab:matlab.internal.language.introspective.errorDocCallback('pde_lun20_2h_walec6prb', 'pde_lun20_2h_walec6prb.m', 152)" style="font-weight:bold">pde_lun20_2h_walec6prb</a> (<a href="matlab: opentoline('pde_lun20_2h_walec6prb.m',152,0)">line 152</a>)

'MassDensity',ro_ult,...

I will be most thankfull for any help in this matter.

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Answer 1

Jan 2021-7-21

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/882978-applying-if-condition-within-location-dependent-thermal-properties#answer_751073

After defining

ro_ult = @(location,state) ro_d-(ro_d-ro_s)*exp(location.y/0.06);

ro_ult is a function handle, which expects two inputs. Then code like this:

ro_ult = ro_ult(location, state);
...  'MassDensity',ro_ult,...     

calls the function ro_ult without input arguments, which produces the shown message.

Calling the output exactly as the name of the function is extremely confusing. Maybe

... 'MassDensity',ro_ult,...

occurs without calling the function ro_ult() before. The function does not contain useful comments also. So it is not clear why it replies a number or a function handle depending on a value. Maybe you mean:

function x = ro_ult(location, state)
% Insert useful comments here...
ro_s = 1300;
ro_d = 1800;
if location.y <= 0
    x = ro_d - (ro_d - ro_s) * exp(location.y / 0.06);
else
    x = 1.6;
end
end