subtracting values in arrays and holding the result

Hi all,

I have 2 vectors (inputs)

    B=[10.81 10.83 10.84 10.93 11.31 11.7 11.7 11.7 11.7 11.7 11.7 11.7 11.7 11.7]';

    lool=[0 0.02 0.01 0.09 0.38 0.39 0 0 0.04 0.24 0.65 0.57 -0.66 -0.54]';

when lool<0 AND B==11.7 I would like to do the calculation B+lool BUT ONLY for the first element that meet these conditions. Then I would like to use the result calculated (in this case 11.7-0.66=11.04) and add the next element from lool that meets these conditions (in this case 11.04-0.54=10.5). The final output I want to get is vector C

C= [10.81
10.83
10.84
10.93
11.31
11.7
11.7
11.7
11.7
11.7
11.7
11.7
11.04
10.5]

thanks

Answer 1

[KSSV]

B=[10.81 10.83 10.84 10.93 11.31 11.7 11.7 11.7 11.7 11.7 11.7 11.7 11.7 11.7]';
lool=[0 0.02 0.01 0.09 0.38 0.39 0 0 0.04 0.24 0.65 0.57 -0.66 -0.54]';
C = B ;
for i = 1:length(B)
    if lool(i) < 0 && B(i)==11.7
        C(i) = B(i)+lool(i) ;
    end
end

Vectorised:

idx = B==11.7 & lool<0 ;
C = B ;
C(idx) = B(idx)+lool(idx) ;

[Jan]

Or:

idx = (B==11.7 & lool<0);
C   = B + idex .* lool;

Then the logical indices FALSE and TRUE are converted to the double values 0 and 1 implicitly.

[Nikolas Spiliopoulos]

thanks for the answer, but It's not what I am looking for. i have already done this. the thing is that the last element should be 10.5 instead of 11.16. So the last calculation should be 11.04-0.54 instead of 11.7-0.54

thanks

[KSSV]

How/Why it is 10.5?

[Nikolas Spiliopoulos]

Because the pevious result should be used(11.04-0.54) instead 11.7-0.54

Thanks!

[Nikolas Spiliopoulos]

11.04 is the result from 11.7-0.66

[Jan]

@Nikolas: I still don't get exactly, what you want to achieve. What is the general instruction to compute the output?

[Nikolas Spiliopoulos]

Let me clarify, when the conditions are true I want to make this calculation: B+lool BUT ONLY for the first element that satisfies the condition. Then, if the conditions are still true I need to use the result of the previous calculation, and add to this the next lool element.

So the last calculation should be 11.04-0.54 instead of 11.7-0.54 Is it now clear?

thanks a lot!!

[Stephen23]

@Nikolas Spiliopoulos: you have now asked about this topic in ten separate questions, each time giving a small tidbit of information that changes the requirements. These vague definitions and explanations, such as "So the last calculation should be 11.04-0.54 instead of 11.7-0.54" do not clarify the general rule, nor do they give us sample input and output data to work with.

It would be a much more effective use of everyone's time if you defined the problem clearly, complete with sample input and output vectors that we can test code on. Please help us to help you by finally writing one clear question with all of the information that we actually need, including the sample input and output vectors.

For example:

"I need to generate from vector X the vector Y:"

 X = [1,2,3,4,...];
 Y = [1,4,7,2,...];

"The rules are that"_

• "if X(k+1)>X(k) then ... "
• "if X(k+1)<X(k) then ...."
• etc.

And then we can finally resolve your task for you.

PS: the sample output vector is important. Do not forget it. We need to be able to use these vectors.

[Nikolas Spiliopoulos]

sorry for being a pain, I am going to edit the question again thanks