indexing with global variables in function statements

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Muazma Ali
Muazma Ali 2017-12-15
评论： Walter Roberson 2017-12-15
Hi! can I not include a global variable in an output in a function like this:
function sigma_v_eff_sona(zone_number,1)=effective_stresses()
when I declare zone_number as global variable in effective_stresses. Do I have to skip the index zone_number in the output statement since I have declared zone_number as a global variable in the mentioned function?

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回答（2 个）

Walter Roberson
Walter Roberson 2017-12-15
The left hand side of the = of a function statement must be plain variables names, not indexed, not structure references, not cell array references.
In MATLAB, if you want to have a function that changes only some portions of the output variable, then the variable must be input as well, such as
function sigma_v_eff_sona = effective_stresses(sigma_v_eff_sona)
global zone_number
sigma_v_eff_sona(zone_number,1) = ...
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Muazma Ali
Muazma Ali 2017-12-15
编辑：Walter Roberson 2017-12-15
ok, this is how it looks like in my script:
zone_number=0;
while .....
zone_number=zone_number+1;
max_pressure=maks_trykk_perm() % this function calls sigma_v_effective_stress=effective_stresses()
in this case where should I preallocate the array called sigma_v_effective_stress?
in my programme i have several such arrays somehow within the while loop but not directly. They are supposed to have max 40 values each.
Walter Roberson
Walter Roberson 2017-12-15
I think you should rewrite as a for loop. Perhaps something similar to
max_zones = 40;
max_pressure = zeros(1, max_zones);
old_max_pressure = inf;
for zone_number = 1 : max_zones
this_pressure = maks_trykk_perm();
if abs( this_pressure - old_max_pressure) < 0.001
break; %close enough to end the loop early?
end
max_pressure(zone_number) = this_pressure;
...
end

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the cyclist
the cyclist 2017-12-15
编辑：the cyclist 2017-12-15
Are you getting the error "Unexpected MATLAB expression"? The global variable is irrelevant. The following is not a valid way to output from a MATLAB function.
function x(1) = answerTest()
x = [3 2];
end
You need to do the indexing in the function, then output a "whole" variable.

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