Error: The expression to the left of the equals sign is not a valid target for an assignment.

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PUPPALA RAJENDHAR 17PHD0038 2019-8-26

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评论： Walter Roberson 2019-8-30

Ycomfort=str2func(strcat('@(x,T_set_r,T_room_m,T_room_mm,DT_m,DT_L,DT_U,T_room,Gt,dc,Q_HVAC,N_slot,T_set_w,dT_L,dT_U,Tw_m,Tw_mm,f_t,G,Bt,Rt,dT_m,T_w,T_env,T_n,Q_CHPU)',Fcomfort));

Error: The expression to the left of the equals sign is not a valid target for an assignment.

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PUPPALA RAJENDHAR 17PHD0038 2019-8-29

Thank you sir for your valuable suggestion. i will try to make a MWE

Walter Roberson 2019-8-29

The most common cause for this problem is that you are in the middle of a [ or { matrix definition, that you forgot a ] or } or accidentally commented it out

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采纳的回答

Stephen23 2019-8-30

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编辑：Stephen23 2019-8-30

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As Walter Roberson already wrote, the problem is most likely caused by unmatched curly braces or square brackets earlier in the code. This error is easy to demonstrate, e.g. in a script which mimics your code flow:

baz = @(a,b)a+b;
str = 'baz(a,b);';
vec = {1,2,; % !!! unmatched curly brace !!!
foo = str2func(strcat('@(a,b)',str));
foo(2,3)

which when run throws exactly the error that you are getting:

>> temp5
Error: File: temp5.m Line: 6 Column: 5
The expression to the left of the equals sign is not a valid target for an assignment.

Here is a much simpler demonstration of this error, showing that the error is unrelated to str2func or strcat or functions in particular:

vec = {1,2,; % !!! unmatched curly brace !!!
foo = 23

giving:

>> temp5
Error: File: temp5.m Line: 5 Column: 5
The expression to the left of the equals sign is not a valid target for an assignment. 

Solution: check your brackets/braces !

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更多回答（1 个）

Mahesh Taparia 2019-8-30

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编辑：Mahesh Taparia 2019-8-30

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Hi,

You can use the below command:

Ycomfort=str2func('@(x,T_set_r,T_room_m,T_room_mm,DT_m,DT_L,DT_U,T_room,Gt,dc,Q_HVAC,N_slot,T_set_w,dT_L,dT_U,Tw_m,Tw_mm,f_t,G,Bt,Rt,dT_m,T_w,T_env,T_n,Q_CHPU)Fcomfort(varargin)'); 

Where Fcomfort is the function of the mentioned variables.

You can refer the below link for more help for str2func:

https://www.mathworks.com/help/matlab/ref/str2func.html

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Stephen23 2019-8-30

编辑：Stephen23 2019-8-30

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"As per my answer, Fcomfort should be a function of the variables which is mentioned in the '@()' ..."

Here is str2func exactly as you used it in your answer:

str2func('@(x,T_set_r,T_room_m,T_room_mm,DT_m,DT_L,DT_U,T_room,Gt,dc,Q_HVAC,N_slot,T_set_w,dT_L,dT_U,Tw_m,Tw_mm,f_t,G,Bt,Rt,dT_m,T_w,T_env,T_n,Q_CHPU)Fcomfort');

and now abbreviated for clarity, showing that you did not call Fcomfort with any input arguments:

str2func('@(x,T_set_r,...,T_n,Q_CHPU)Fcomfort');
%                                    ^^^^^^^^^ Fcomfort does not use any of the variables

"Where Fcomfort is the function of the mentioned variables."

Can you show an example of this working? When I try your advice it fails:

>> F = str2func('@(a,b)baz');
>> F(1,3)
Error using baz (line 2)
Not enough input arguments.
Error in @(a,b)baz

Where baz is "a function of the variables which is mentioned in the '@()'" exactly as you specified:

function z = baz(a,b)
z = a+b;
end

Or even simply:

>> baz = @(a,b)a+b;
>> F = str2func('@(a,b)baz');
>> F(0,1)
Undefined function or variable 'baz'.
Error in @(a,b)baz

"Your command format is incorrect"

Why? It works perfectly when I tried it:

>> baz = @(a,b)a+b;
>> fun = 'baz(a,b)';
>> foo = str2func(strcat('@(a,b)',fun));
>> foo(2,3)
ans =
     5

Rik 2019-8-30

@Mahesh can you try to make an example with your syntax that can actually run without errors? Whenever I get questioning comments from other users, I always make sure that the code I'm suggesting runs at least on my system.

Walter Roberson 2019-8-30

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You can code

Ycomfort=str2func('@(x,T_set_r,T_room_m,T_room_mm,DT_m,DT_L,DT_U,T_room,Gt,dc,Q_HVAC,N_slot,T_set_w,dT_L,dT_U,Tw_m,Tw_mm,f_t,G,Bt,Rt,dT_m,T_w,T_env,T_n,Q_CHPU)Fcomfort(x,T_set_r,T_room_m,T_room_mm,DT_m,DT_L,DT_U,T_room,Gt,dc,Q_HVAC,N_slot,T_set_w,dT_L,dT_U,Tw_m,Tw_mm,f_t,G,Bt,Rt,dT_m,T_w,T_env,T_n,Q_CHPU)');

but remember that the effect of that would be to index the character vector fcomfort, not execute a function named fcomfort.

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