Re: Ploting a simple graph

On 2013-07-17 15:12:01 +0000, dpb said:

> On 7/17/2013 3:36 AM, Tiger wrote:
>> On 2013-07-16 16:05:13 +0000, Nasser M. Abbasi said:
>> On 7/16/2013 10:39 AM, Tiger wrote:
> ...
>> I would like to draw a y=x graph where y=0 if x<0.5. So the graph
>> should be flat until x is greater than 0.5 and then a 45 degree line
>> onwards. I used the code below but I cannot seem to achieve what I want
>> to achieve. Where would be my mistake?
>>
>> x=0.1:0.01:1;
>> if (x<0.5)
>> y=0;
>> else
>> y=x;
>> end
>> figure(1), plot(x,y);
> ...
>
>>
>> f = @(x) x.*(x>=0.5);
>> x = 0.1:0.01:1;
>> plot(x,f(x))
> ...
>
>> Thank you. I will study the code, in particular the " = @(x) x.*(x>=0.5)"
>> part. But why my approach is not healthy? What is the logical mistake I
>> am making? Could you please briefly comment?
>
> The " = @(x) x.*(x>=0.5)" is an anonymous function. Look up them in
> the doc search for details.
>
> The logic flaw in your approach is that in Matlab, the IF condition is
> T _iff_ all elements in the condition vector/array are T -- in this
> case that is not so. So, the ELSE clause is all that's evaluated.
>
> doc IF for details there...
>
> One alternate way to write you condition would be
>
> y=x; y(x<0.5)=0;
>
> In the above, the logical array from the test is used an a logical
> addressing expression (look that up, too) and then the locations that
> are T by position are assigned the RHS.
>
> I suggest going to the doc an reading the "Getting Started" section
> linearly to begin to get a feel for how to use Matlab and the basic
> ideas of how it's implemented.

Thank you very much for the explanations and the advice!