Running if loop until a specific outcome

I have two double vectors, a and b. Both have values for each time point t. I want to run a loop where

• -for each time t,
• --if a >= 0.5 and the next value that is >=0.5 is in a, outa = outa + 1
• --if a >= 0.5 and the next value that is >=0.5 is in b, outc = outc + 1
• --if b >= 0.5 and the next value that is >=0.5 is in b, outb = outb + 1
• --if b >= 0.5 and the next value that is >=0.5 is in b, outc = outc + 1

How might I be able to do this?

[Image Analyst]

datasets are deprecated. What is the class of your a and b? Are they really "dataset" variables, or simple double vectors (hopefully), or something else (structure arrays, tables, etc.)? What does this show:

whos a
whos b

[numnum]

 they are double vectors. 
whos a/b yields
Name: v1
Size: 1x2000000
Bytes: 16000000
Class:double

[numnum]

when i try this:

[i,j,v] = find(a>=0.5); 
[k,l,m] = find(b>=0.5);

for ix=(2:max(length(i),length(k)))
outa=0;
outb=0;
outc=0;
if i(ix) < k(ix) && i(ix+1) < k(ix)
    outa=outa+1;
end
if  i(ix) < k(ix) && i(ix+1) > k(ix)
    outc=outc+1;
end
if i(ix) > k(ix) && i(ix+1) < k(ix)
    outc=outc+1;
end
if  i(ix) > k(ix) && i(ix+1) > k(ix)
    outb=outb+1;
end

end

I get the error Index exceeds matrix dimensions.

Error (line 129) if i(ix) < k(ix) && i(ix+1) < k(ix)

Answer 1

[Image Analyst]

Evidently i and k are different lengths, so that when ix goes from 2 to max(length(i),length(k)), it will be too long for the shorter of those two vectors. Before the loop put this:

length(i)
length(k)
max(length(i),length(k))

Then tell me what is is when it throws the error (look in the workspace panel).

[numnum]

thank you! If you mean the values, length(i)= 48680 and length(k)= 219533

[Image Analyst]

OK, so at some point, since ix runs from 2 to 219533, ix will take on the value of 48681 (one longer than i is). So when it does this

if i(ix) < k(ix) && i(ix+1) < k(ix)

which means

if i(48680) < k(48680) && i(48680+1) < k(48680)

Now i(48680+1) is i(48681). And since there is no 48681st element of (the badly named) i, it will thrown an error.

[numnum]

Yeah they are pretty badly named.

Is there a way I can fix this, while still running through all of k's 219533 values?

there also seems to be another problem because my code outputs outa=0 outb=1 outc=0 , which is very far off from the values i should get