How to plus between indices?

Vec = [0 -0 0 -0 0 0 0 0 1 0 0 0 -0 3 4 0 -0 0 0]

First step find non-zero value.

[Vecindex] = find(abs(Vec)>0)
 Vecindex= 9 14 15

Q1. How to plus between indices?

• 1+0 (indices is 9 and 10)
• 3+4 (indices is 14 and 15)

[Roger Stafford]

Please expand on your phrase “How to plus between indices”. I don’t know what you mean by that. Show a vector with a larger number of non-zero values and the result you expect, in order to demonstrate what you mean.

[DongShin Yang]

I want to revise vector value and index.

A = [ 0 0 0 0 2 0 0 0 1 4 0 0 ]

Revised A is that

A = [ 0 0 0 0 2 0 0 0 5 0 0 0 ]

The indices and value were revised by

2 index(5) + 0(index(6)next to value )

1(10) + 4(11) = 5 and index (10)

[Guillaume]

Note that

find(Vec)  %no need for abs(Vec)>0

is sufficient to find the indices of non-zero values

Also note that matlab does not have a concept of negative zero.

Finally, what should happen with:

Vec = [0 1 0 0 3 4 6 0 0]

Are the 3 4 6 all summed together or just 3 and 4?

[Roger Stafford]

@Guillaume: Actually, because most computers that run Matlab adhere to the 754 IEEE Standard for Binary Floating-Point Arithmetic, these do have the concept of a negative zero. You can tell the difference between the two kinds of zero by dividing 1 by them. A plus zero will give inf and a minus zero will produce -inf. Also fprintf will exhibit a minus sign on minus zero. Using format hex also reveals the difference.

Answer 1

[Walter Roberson]

strfind(Vec, [1 0])
strfind(Vec, [3 4])

[DongShin Yang]

Thank your help. But because of rack of my explain. Your answer was different. Sorry. I want to find non-zero value and indice and Plus first one and next one, then, Revise index of result of plus.