Oscar and Mats,
Thank you for your comments and taking time to look at the snips.
Yes, I think I had commented that the avg+trigger was = triggervolts in my
original post.
I did find that there was an intermediary process which I had forgotten to
comment out that was adversely affecting the data in one instance and not
the other. So it WAS a case of becoming code blind. But I didn't give
y'all all of the code so you would not have known that. My apologies.
Mats, I'd like to get a better handle on your suggestions about improving
the code. Turns out, I've got another couple of 4GByte files to sift
through, and they are less 'friendly' when it comes to determining the
start and stop points. So, I have to basically redo about half of my code
and I'd like to improve on my Python coding skills.
Unfortunately, I have gaps in my coding time, and I end up forgetting the
details of a particular language, especially a new language to me, Python.
I'll admit that my 'C' background keeps me thinking as these data sets as
arrays.. in fact they are lists, eg:
[
[t0, v0],
[t1, v1],
[t2, v2],
.
.
.
[tn, vn]
]
Time and volts are floats and need to be converted from the csv file
entries.
I'm not sure that follow the "unpack" assignment in your example of:
for row in TrigWind:
time, voltage = row # unpack
I think I 'see' what is happening, but when I read up on unpacking, I see
that referring to using the * and ** when passing arguments to a function...
I tried it anyhow, with this being an example of my source data:
"Record Length",2000002,"Points",-0.005640001706,1.6363
"Sample Interval",5e-09,s,-0.005639996706,1.65291
"Trigger Point",1128000,"Samples",-0.005639991706,1.65291
"Trigger Time",0.341197,s,-0.005639986706,1.60309
,,,-0.005639981706,1.60309
"Horizontal Offset",-0.00564,s,-0.005639976706,1.6363
,,,-0.005639971706,1.65291
,,,-0.005639966706,1.65291
,,,-0.005639961706,1.6363
.
.
.
Note that I want the items in the third and fourth column of the csv file
for my time and voltage.
When I tried to use the unpack, they all came over as strings. I can't
seem to convert them selectively..
Desc1, Val1, Desc2, TimeVal, VoltVal = row
TimeVal and VoltVal return type of str, which makes sense.
Must I go through yet another iteration of scanning TimeVal and VoltVal and
converting them using float() by saving them to another array?
Thanks for your patience.
Chip
On Sat, Jul 13, 2019 at 9:36 AM Mats Wichmann <m...@wichmann.us> wrote:
> On 7/11/19 8:15 AM, Chip Wachob wrote:
>
> kinda restating what Oscar said, he came to the same conclusions, I'm
> just being a lot more wordy:
>
>
> > So, here's where it gets interesting. And, I'm presuming that someone
> out
> > there knows exactly what is going on and can help me get past this
> hurdle.
>
> Well, each snippet has some "magic" variables (from our point of view,
> since we don't see where they are set up):
>
> 1: if(voltage > (avg + triglevel)
>
> 2: if((voltage > triggervolts)
>
> since the value you're comparing voltage to gates when you decide
> there's a transition, and thus what gets added to the transition list
> you're building, and the list size comes out different, and you claim
> the data are the same, then guess where a process of elimination
> suggests the difference is coming from?
>
> ===
>
> Stylistic comment, I know this wasn't your question.
>
> > for row in range (len(TrigWind)):
>
> Don't do this. It's not a coding error giving you wrong results, but
> it's not efficient and makes for harder to read code. You already have
> an iterable in TrigWind. You then find the size of the iterable and use
> that size to generate a range object, which you then iterate over,
> producing index values which you use to index into the original
> iterable. Why not skip all that? Just do
>
> for row in TrigWind:
>
> now row is actually a row, as the variable name suggests, rather than an
> index you use to go retrieve the row.
>
> Further, the "row" entries in TrigWind are lists (or tuples, or some
> other indexable iterable, we can't tell), which means you end up
> indexing into two things - into the "array" to get the row, then into
> the row to get the individual values. It's nicer if you unpack the rows
> into variables so they can have meaningful names - indeed you already do
> that with one of them. Lets you avoid code snips like "x[7][1]"
>
> Conceptually then, you can take this:
>
> for row in range(len(Trigwind)):
> voltage = float(TrigWind[row][1])
> ...
> edgearray.append([float(TrigWind[row][0]),
> float(TrigWind[row][1])])
> ...
>
> and change to this:
>
> for row in TrigWind:
> time, voltage = row # unpack
> ....
> edgearray.append([float)time, float(voltage)])
>
> or even more compactly you can unpack directly at the top:
>
> for time, voltage in TrigWind:
> ...
> edgearray.append([float)time, float(voltage)])
> ...
>
> Now I left an issue to resolve with conversion - voltage is not
> converted before its use in the not-shown comparisons. Does it need to
> be? every usage of the values from the individual rows here uses them
> immediately after converting them to float. It's usually better not to
> convert all over the place, and since the creation of TrigWind is under
> your own control, you should do that at the point the data enters the
> program - that is as TrigWind is created; then you just consume data
> from it in its intended form. But if not, just convert voltage before
> using, as your original code does. You don't then need to convert
> voltage a second time in the list append statements.
>
> for time, voltage in TrigWind:
> voltage = float(voltage)
> ...
> edgearray.append([float)time, voltage])
> ...
>
>
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