CODEWITHSUNDEEP
pythonnumpy
Justin
Justin

Reputation: 87

Deleting elements in a row

I want to get an answer for c where c is defined as:

c= x+y

I have the following entry for x and y:

x y
-2 5
-3 10
2 15
4 20
6 25

to get the data, I loaded it from a csv file:

data=np.loadtxt('data.csv',delimiter=',',skiprows=1)
x_value= data[:,0]
y_value= data[:,1]

The code works fine until I decided to remove the negative entry for x. I have:

x_value1= [x for x in x_value if float(x)>0]

It now returns an error. I understand that for it to work, I also have to remove 5 and 10 in y since the entries for the equation are not the same. I don't have any idea how should I do it.

Upvotes: 0

Views: 46

Answers (3)

Ashalynd
Ashalynd

Reputation: 12563

Probably you can try something like:

data[data[:,0]>0]

as hinted in the similar answer:filtering lines in a numpy array according to values in a range

Upvotes: 1

Ben
Ben

Reputation: 2133

Use your logic on data instead, checking for negative on the first entry of each 2-tuple:

>>> data
array([[-2,  5],
       [-3, 10],
       [ 2, 15],
       [ 4, 20],
       [ 6, 25]])

>>> data2 = n.array([x for x in data if float(x[0])>0]) # x here is each row
>>> data2
array([[ 2, 15],
       [ 4, 20],
       [ 6, 25]])

Upvotes: 1

TheSoundDefense
TheSoundDefense

Reputation: 6935

You're probably going to want to ditch the list comprehension for this, since it's a longer operation and it will involve multiple lists. You could just use indices, and copy the non-negative data into new lists:

new_x = []
new_y = []
for i in range(len(x)):
  if x[i] >= 0:
    new_x.append(x[i])
    new_y.append(y[i])

Alternate strategy using zip:

new_x = []
new_y = []
for x_elem, y_elem in zip(x,y):
  if x_elem >= 0:
    new_x.append(x_elem)
    new_y.append(y_elem)

I'm not sure if there's a more condensed way of doing this, but I prefer longer, more readable code anyway.

Upvotes: 1

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