Where is the problem

Hi, I got this error:

In an assignment  A(:) = B, the number of elements in A and B must be the same.

UserData.info(4,2)=num2cell(sym(strcat('u',sym(UserData.matrix{4,2}))));

UserData.info and UserData.matrix are cell type.

I don't understand, where is problem?

[Walter Roberson]

I don't know what it would mean to strcat a string and a symbol. Unfortunately I do not have the toolbox to test with.

Answer 1

[per isakson]

Try

UserData.info{ 4, 2 } =num2cell(sym(strcat('u',sym(UserData.matrix{4,2}))));

--- next ---

It is easier to debug and understand with one step per line:

    temp1 = UserData.matrix{4,2};
    temp2 = sym(temp1);
    temp3 = strcat( 'u', temp2 );
    temp4 = sym( temp3 );
    temp5 = num2cell( temp4 );

    UserData.info{ 4, 2 } = temp5;

    whos temp*

.

--- next 2 ---

Is strcat supposed to concatenate a character, 'u' and something of class sym? What is this strcat-line supposed to do?

.

--- next 3 ---

Run this function and note that strcat fails when temp2 == 10. '10' is displayed on screen before the error message.

    function cssm

temp1 = UserData.matrix{4,2};

    for temp1 = 3 : 23
        temp2 = sym(temp1);
        try 
            temp3 = strcat( 'u', temp2 );
        catch me
            disp( temp2 )
            rethrow( me )
        end

        temp4 = sym( temp3 );
        temp5 = num2cell( temp4 );

        UserData.info{ 4, 2 } = temp5;
    end
    whos temp*

    end

    >> cssm
    10
    In an assignment  A(:) = B, the number of elements in A and B
    must be the same.
    Error in strcat (line 95)
            s(pos:pos+len-1) = str;
    Error in cssm (line 7)
            temp3 = strcat( 'u', temp2 ); 
    >>

The reason is that length( temp2 ) always returns 1. Thus, it works for one digit numbers, but not for 10 or 23.

My conclusions are:

1. the function, strcat, is made for strings only
2. all the numerical stuff in Matlab isn't tested with sym class input. At Mathworks they didn't anticipate that someone would through sym at strcat :-).

[john]

Sorry,, but this code doesn't work :-(

[Oleg Komarov]

Saying it doesn't work really doesn't help to understand what's going on. Be more specific, and post any error message you get.

[john]

this is the error message:

??? In an assignment A(:) = B, the number of elements in A and B

must be the same.

Error in ==> strcat at 96

s(pos:pos+len-1) = str;

Error in ==> menu>pushbutton12_Callback at 2563

UserData.info{ 4, 2 } =num2cell(sym(strcat('u',sym(UserData.matrix{4,2}))));

Error in ==> gui_mainfcn at 96

feval(varargin{:});

Error in ==> menu at 42

gui_mainfcn(gui_State, varargin{:});

Error in ==>

@(hObject,eventdata)menu('pushbutton12_Callback',hObject,eventdata,guidata(hObject))

??? Error while evaluating uicontrol Callback

[john]

if UserData.matrix{4,2} is only one number like 5, then it is ok, but if UserData.matrix{4,2} is bigger number like 23, then I got error message

[Walter Roberson]

When UserData.matrix{4,2} is a larger number like 23, then try

T1 = sym(UserData.matrix{4,2});

class(T1), size(T1)

T2 = strcat('u', T1);

class(T2), size(T2)

I have suspicions, but I do not have any way to test them myself.

[john]

Walter, if UserData.matrix{4,2} is like 3, then class(T1)=sym, and size(T1)=1,1 ; and all is OK

;

;

but if UserData.matrix{4,2} is like 34, then also class(T1)=sym, and size(T1)=1,1, ;, but from T2 = strcat('u', T1); I got error

[john]

problem is command sym.......T1 = sym(UserData.matrix{4,2});,,,,,,strcat has problem with sym,

,

,

,

easy example ......try strcat('d',sym('4')) and strcat('d',sym('45'))

[Walter Roberson]

So perhaps it should be

UserData.info{ 4, 2 } =num2cell(sym(strcat('u',char(sym(UserData.matrix{4,2})))));

Question: what data types are likely to occur in the UserData.matrix elements that you would use?

[john]

into UserData.matrix I write by thes way: UserData.matrix(4,4)=num2cell(sym(get(handles.edit7,'string')));

[john]

great......it works ....UserData.info{ 4, 2 } =num2cell(sym(strcat('u',char(sym(UserData.matrix{4,2})))));

big thank you ..

.

.

you help me a lot of time, how can I thank you?

[Walter Roberson]

All those sym() conversions give the impression that you are converting back and forth more often than you need to.