Please how can i use generate a formula in pandas

Question

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df['weight_MA']= (Pn ​ ∗W1 ​ )+(Pn−1 ​ ∗W2 ​ )+(Pn−2 ​ ∗W3 ​ )... / ∑W ​

where: P = Price for the period n = The most recent period, n-1 is the prior period, and n-2 is two periods prior W = The assigned weight to each period, with the highest weight going first and then descending linearly based on the number of periods being used ​

Please how can i use that formula in pandas to get something like

((P5 * 5)+(P4 *4)+(P3 *3)+(P2 *2)+(P1 *1)) / (5+4+3+2+1)

Let’s say that the price of this stock fluctuates as so:

Day 5: $90.90

Day 4: $90.36

Day 3: $90.28

Day 2: $90.83

Day 1: $90.91

df['weight_MA'] = ((90.90 *5)+(90.36 *4)+(90.28 *3)+(90.83 *2)+(90.91 *1)) / (5+4+3+2+1) =

Answer 1

weight = numpy.array([1,2,3,4,5])
df = pandas.DataFrame([90.91,90.83,90.28,90.36,90.90])

df['weight_MA'] = df.rolling(weight.shape[0]).apply(lambda x: numpy.sum(x * weight) / numpy.sum(weight))

rolling gives you a dataframe consisting of the previous n row value. Then, applying a lambda function to multiply df and your weight, and divided by the sum of weight.