Extract the indices for a set of repeating data in a list-CodePudding

I have a list of angles that always start with -90 to 90, but some of the data may have more or less values in between the start and end points. The list would look something like this:

Angles = [-90, -60, -30, 0, 30, 60, 90, -90, -45, 0, 45, 90, -90, -60, -45, 0, 45, 60, 90]

I have another list with corresponding values to these angles that I want to pull without having to know the indices for the entire segment since the amount of number between the -90 and 90 may change.

For example, if we call:

Angles[0:7] that should report [-90, -60, -30, 0, 30, 60, 90]

Angles[7:12] that should report [-90, -45, 0, 45, 90] and so on and so forth.

I have another list called "data" which have corresponding variables to the angles.

data = [50, 120, 0, 75, 231, 623, 30, 40, -45, 0, 3215, 955, 40, -440, -45, 210, 445, 660, 190]

Essentially I want a script that can grab the indices of all the angles and corresponding data points. It would go through the Angles variable and separate out the points from -90 to 90, then it would grab the indices (let's say Angles[0:7], Angles[7:12], etc) and would allow us to put the corresponding data points into a new variable. Segment1 = data[0:7], Segment2 = data[7:12]. I can't hardcode the exact indices since the number of points in a -90 to 90 sweep may change.

I have tried to modify one of the answers from here: Python finding repeating sequence in list of integers? but this was using multiple lists. Could not try to understand how to use it within the same list.

CodePudding user response：

Here is one way you could do it:

# create empty list to store indices
indices = []

# create empty list to store segments
segments = []

# keep track of the current segment
current_segment = []

# iterate over the angles in the Angles list
for i, angle in enumerate(Angles):
    # if the current angle is -90, start a new segment
    if angle == -90:
        current_segment = []
        indices.append(i)
    # if the current angle is 90, end the current segment
    elif angle == 90:
        current_segment.append(i)
        segments.append(current_segment)
    # otherwise, just add the index to the current segment
    else:
        current_segment.append(i)

# now you can use the indices to grab the corresponding data points
# using the indices list, you can create the segments as follows:
segment1 = data[indices[0]:indices[1]]
segment2 = data[indices[1]:indices[2]]

Here, segment1 will be a list containing the data points corresponding to the angles in the first segment of Angles, segment2 will be a list containing the data points corresponding to the angles in the second segment of Angles, and so on.

CodePudding user response：

It's a bit dirty logic but this is what can help you immediately

lsit_value = [-90, -60, -30, 0, 30, 60, 90, -90, -45, 0, 45, 90, -90, -60, -45, 0, 45, 60, 90]


def test(lsit_value):
    x = 0
    couples = []
    result = []
    for i in lsit_value:
        if i == -90 :
            couples.append(x)   
        elif i == 90:
            couples.append(x)
            result.append(list(couples))
            couples.clear()
        x = x 1
    return result


print(test(lsit_value))

result of print [[0, 6], [7, 11], [12, 18]]