Question about my code for adding 'price_criterion' column

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#1

Hi,

I am stuck on my code for course 467-6. Apologies I could not tag the course for some reason.

Screen Link:
https://app.dataquest.io/m/467/communicating-results/6/price-vs-rating

My Code: 

cheap = affordable_apps["Price"] < 5
reasonable = affordable_apps["Price"] >= 5
cheap_mean = affordable_apps[cheap]['Price'].mean()
reasonable_mean = affordable_apps[reasonable]['Price'].mean()

affordable_apps['price_criterion'] = affordable_apps[cheap]['Price'].apply(
lambda x: 1 if x < cheap_mean else 0)

affordable_apps['price_criterion'] = affordable_apps[reasonable]['Price'].apply(
lambda x: 1 if x < reasonable_mean else 0)

I was expecting to fill the affordable_apps[‘price_criterion’] table with the correct value of 1 or 0. But for some reason for it does not fill for the “cheap” boolean mask.

Thank you for your help!

#2

Can you include your definition for cheap_mean and reasonable_mean

#3

Here you are replacing price_criterion it should be assigning only cheap first and second time reasonable for that you can use loc

affordable_apps.loc[cheap, 'price_criterion'] = affordable_apps[cheap]['Price'].apply(
lambda x: 1 if x < cheap_mean else 0)

affordable_apps.loc[reasonable, 'price_criterion'] = affordable_apps[reasonable]['Price'].apply(
lambda x: 1 if x < reasonable_mean else 0)

For later part instead of apply you can do

affordable_apps.loc[cheap, 'price_criterion'] = (affordable_apps[cheap]['Price'] < cheap_mean).astype(int)

affordable_apps.loc[reasonable, 'price_criterion'] = (affordable_apps[reasonable]['Price'] < reasonable_mean).astype(int)
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#4

@YoussefAlaaEtman I just included it!

#5

@DishinGoyani thank you for the answer, I understand that is the same answer provided in the exercise.

However, may you explain why my code doesn’t work? I thought writing affordable_apps[cheap][‘Price’].apply() would help filter the columns within price_criterion. Is there a way to write my code to make it work?

#6

Expression on right hand side is correct but issue is in left hand side (While assigning result to column)

Both time you are using affordable_apps['price_criterion'] = ... that will replace all column instead of altering only cheap rows. To made it only change cheap rows we will need to pass boolean index on left hand side. like affordable_apps.loc[cheap, 'price_criterion'] = ... so only cheap rows get alter. and the same for reasonable rows.

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#7

Okay I see, thank you so much!

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