Thread Subject:

usage of " . " in these two equations !!!

Dear all,
I got the following error message:

??? Error using ==> mrdivide
Out of memory. Type HELP MEMORY for your options.

Error in ==> weather4Elora at 57
ec_sh_06=0.622*ec_es_06/(ec_p_06-0.378*ec_es_06);


However, I thought I probably the equation need to be modified to the following one.
ec_sh_06=(0.622.*ec_es_06)./(ec_p_06-0.378.*ec_es_06);

What is the difference between these two equations? Why do we need to put a " . " behind numbers? Can you guys help me to under this usage?

Thanks,
Michael

"Kuo-Hsien" <mchangks@hotmail.com> wrote in message
> What is the difference between these two equations? Why do we need to put a " . " behind numbers? Can you guys help me to under this usage?


The dot is read as 'element-by-element' when used like this. Study an easy example if it is still unclear to you.

A = magic(2)
A^2
A*A
A.^2

Now, which one to use in your application will depend on what you are trying to do.




M`Ekbe[W&MOkkakQ\Q9kkr[rTQ1[`kN`UXyMTMYk\NMZT[[SOUX,[QaMMYZ

"Matt Fig" <spamanon@yahoo.com> wrote in message <gng046$quc$1@fred.mathworks.com>...
> "Kuo-Hsien" <mchangks@hotmail.com> wrote in message
> > What is the difference between these two equations? Why do we need to put a " . " behind numbers? Can you guys help me to under this usage?
>
>
> The dot is read as 'element-by-element' when used like this. Study an easy example if it is still unclear to you.
>
> A = magic(2)
> A^2
> A*A
> A.^2
>
> Now, which one to use in your application will depend on what you are trying to do.
>
>
>
>
> M`Ekbe[W&MOkkakQ\Q9kkr[rTQ1[`kN`UXyMTMYk\NMZT[[SOUX,[QaMMYZ


For more information regarding MATLAB operators, go to the Section titled "Operators" at the following web address:

http://www.mathworks.com/access/helpdesk/help/techdoc/matlab.html

"Kuo-Hsien" <mchangks@hotmail.com> wrote in message <gnftna$jud$1@fred.mathworks.com>...
> Dear all,
> I got the following error message:
>
> ??? Error using ==> mrdivide
> Out of memory. Type HELP MEMORY for your options.
>
> Error in ==> weather4Elora at 57
> ec_sh_06=0.622*ec_es_06/(ec_p_06-0.378*ec_es_06);
>
>
> However, I thought I probably the equation need to be modified to the following one.
> ec_sh_06=(0.622.*ec_es_06)./(ec_p_06-0.378.*ec_es_06);
>
> What is the difference between these two equations? Why do we need to put a " . " behind numbers? Can you guys help me to under this usage?
>
> Thanks,
> Michael

Besides what others have already replied, you don't "need" the dots behind numbers (scalars). But you do "need" them before the slash (divide) in your case above.

Here is my test as below. By the way, I deeply thank those who advice me in Matlab.

So, I need to put a "." before any divides, not after scalers.
 

>> ec_es_06=[1;2;3;4;5]
>> ec_p_06=[4;5;6;7;8]
>> nodot=0.622*ec_es_06/(ec_p_06-0.378*ec_es_06)

nodot =

         0 0 0 0 0.1018
         0 0 0 0 0.2036
         0 0 0 0 0.3054
         0 0 0 0 0.4072
         0 0 0 0 0.5090
>> number_dot=(0.622.*ec_es_06)./(ec_p_06-0.378.*ec_es_06)

number_dot =

    0.1717
    0.2931
    0.3835
    0.4534
    0.5090

>> divide_dot=(0.622.*ec_es_06)./(ec_p_06-0.378*ec_es_06)

divide_dot =

    0.1717
    0.2931
    0.3835
    0.4534
    0.5090