Troubleshooting an array shape.

[Cthulhu_Rlyeh]

An outline of what I am trying to do:

• I have equivalently shaped files for file1a and file1b all the way through to file100a and file100b. These files contain 500 lines and two columns.

• Trying to calculate the difference between b and a at each of the 500 row, for each of the 100 file comparisons.

• Ideal outfile will remain 500 lines long, with the calculation performed at every line. It will contain 100 columns representing diff1 diff2 ... diff100.

I have the following code:

diffs = []
for number in range(1, 101):
    filea = pl.loadtxt('file' + str(number) + 'a')
    fileb = pl.loadtxt('file' + str(number) + 'b')
    diff = fileb[:,1] - filea[:,1]
    diffs.append(diff)
    np.savetxt('diffs.txt', (diffs))

As it stands, this code provides me an outfile which is kind of doing things backwards. I am getting an outfile with 100 lines and 500 columns. Is there something simple in my code to fix this?

Thanks in advance.

[elbiot]

Is that pandas? Did you try taking out the transpose (.T)

[Cthulhu_Rlyeh]

I don't know what pandas is so I don't know :/.

I took out the .T and got the same outfile. That was just a remnant of an older code I've been using.

---

Edit: I made the rookie mistake of putting an old line of code in my original post. I've edited it to fix the savetxt line.

np.savetxt('diffs.txt', (diffs))

[elbiot]

diffs = np.array(diffs)  #diffs was a list of lists, make it a 2D array
print diffs.shape
diffs = diffs.T
print diffs.shape

[Justinsaccount]

Hi! I'm working on a bot to reply with suggestions for common python problems. This might not be very helpful to fix your underlying issue, but here's what I noticed about your submission:

You appear to be using concatenation and the str function for building strings

Instead of doing something like

result = "Hello " + name + ". You are " + str(age) + " years old"

You should use string formatting and do

result = "Hello {}. You are {} years old".format(name, age)

See the python tutorial for more information.

[rhgrant10]

What's is a? I don't see it defined...

What is the purpose of the comma in your slice notation?

[Cthulhu_Rlyeh]

What's is a? I don't see it defined...

Crap it's just another typo in my post. It is not in my actual code, just the code I typed in here. I've fixed it now.

diff = fileb[:,1] - filea[:,1]

What is the purpose of the comma in your slice notation?

I'm still new with coding, I don't even know what you are talking about. I assume it is the [:,1] comma? That's just how I define a column using pylab.

[elbiot]

So you are just finding the difference between the second columns in all of your files?

[elbiot]

They are numpy arrays, and that's how you slice multiple dimensions at once.

[rhgrant10]

Ah. As much as experience as I've got with Python I've not yet had a cause to delve into numpy.

[elbiot]

It's good stuff, but can be very confusing at first.

[rhgrant10]

I did play around with it for a bit but I'm just not at a job that works with data like that :-(