So in Python, I would do something like this:
count = sum([a<0 and b>=0 for a,b in zip(countlist,countlist[1:])])
I am having a bit of trouble Googling for this, since I do not know the
right keywords to use, but is there a means of doing something similar with
a list comprehension in Julia?
On Wednesday, July 30, 2014 6:17:18 PM UTC-4, Leah Hanson wrote:
>
> Your problem is with the first index (`i == 1`). You can't check if the
> previous element is < 0. You could adjust your range (the
> `1:length(outputarray)`) to only run through elements for which your
> if-condition makes sense.
>
> -- Leah
>
>
> On Wed, Jul 30, 2014 at 5:12 PM, <[email protected] <javascript:>> wrote:
>
>> I'm a bit stuck on this one. Could I get one more hint about a way I
>> could get the same thing done without using the illegal indexing?
>>
>> On Wednesday, July 30, 2014 5:46:58 PM UTC-4, John Myles White wrote:
>>
>>> Yeah, it’s the combination of (a) the use of i and i+1 indexing with (b)
>>> the use of a loop that goes from i = 1 to i = length(outputarray).
>>>
>>> — John
>>>
>>>
>>> On Jul 30, 2014, at 2:44 PM, [email protected] wrote:
>>>
>>> To correct the bug, is it this?
>>>
>>> if outputarray[i] < 0 && outputarray[i+1] >= 0
>>> count += 1
>>> end
>>>
>>> Factoring in that Julia begins indexing from 1.
>>>
>>> On Wednesday, July 30, 2014 4:41:43 PM UTC-4, John Myles White wrote:
>>>>
>>>> This pseudocode almost works. Just replace Int64[1:len(outputarray)]
>>>> with 1:length(outputarray).
>>>>
>>>> There’s also a bug in your core logic, but I’ll leave fixing that as an
>>>> exercise to the reader.
>>>>
>>>> — John
>>>>
>>>> On Jul 30, 2014, at 1:03 PM, [email protected] wrote:
>>>>
>>>> Hi guys,
>>>>
>>>> I asked this in a previous thread, but because that diverged off-topic
>>>> from my existing question, I decided to create a new thread.
>>>>
>>>> Anyhow, say I have an array
>>>>
>>>> outputarray = Float64[-1.23423,-3.23423,-2.34234,-2.12342,1.23234,2.
>>>> 23423,-2.23432,5.2341,0.01111,1.23423]
>>>>
>>>> This array lists the output of some function. I want to count the
>>>> number of times that the function passes by or equals 0 while emerging
>>>> from
>>>> a negative f(x).
>>>>
>>>> In pseudocode, I want to do:
>>>>
>>>> function counter(outputarray)
>>>> count = 0
>>>> for i in Int64[1:len(outputarray)]
>>>> if outputarray[i] >= 0 && outputarray[i-1] < 0
>>>> count += 1
>>>> end
>>>> end
>>>> return count
>>>> end
>>>>
>>>> What would be the most efficient way of doing this in Julia?
>>>>
>>>> Thanks,
>>>> Wally
>>>>
>>>>
>>>>
>>>
>
