# Weekly Challenge

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## Challenge #185: Amplify your Learning with Weekly Challenges!

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8 - Asteroid

OK, really really glad to have this dataset. Visited London for the first time this past May and while on a riverboat on the Thames, Tower Bridge opened to let through a cruise ship coming up river. A tour guide on our boat was very loud and adamant that this was an incredibly rare event - it only happens a couple dozen times per year, she said. Some simple googling in the moment proved that wasn't true, and maybe we just didn't understand what she was saying was so rare. Glad to see that the data shows it isn't very rare at all!

But this did take me awhile, particularly the tricky interpretation issue with the bonus question. Finally got around to it though.

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7 - Meteor

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12 - Quasar

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8 - Asteroid

Wish I was there in London with everyone!

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13 - Pulsar

I wish I was at #Inspire19 in London!  But at least my new license plates are here:

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8 - Asteroid

My solution attached.

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14 - Magnetar
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Not sure maintenance list counts as a vessel, but here's my solution...
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Alteryx

Solution attached. Spent a while on the bonus question since I didn't see the logic. I understand the method proposed in the solution, but don't agree that it will give us the most likely time to see a lift.

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When you average the dates and times, you are ignoring years when there were no lifts at that time. There were 12 lifts in the 2pm hour on August 30, 2015. There were no lifts in any other 2pm hour on a Sunday in August in any year under consideration. So you get an average of 12, but only one hour in the entire period when there are lifts. On the other hand, there were 15 lifts across 13 different Thursdays in the 5pm hour in 2015, 2016, 2017, and 2018. So the way I see it, based purely on these observations, you have about a 1/16 chance of seeing a lift at 2pm on a Sunday in August and about a 3/4 chance of seeing a lift at 5pm on a Thursday in September.
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8 - Asteroid

Nice challenge!

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Alteryx Certified Partner

I think that either the bonus answer as provided is not correct, or if that is the desired answer, the bonus question ought to be reworded. The given solution suggests that the 2pm hour on Sundays in August is a good time to see the lift, but really it was just very busy during the 2pm hour on a single August Saturday (2015-08-30) and was never in operation during that hour/month/day combination at any other point in the dataset, thus giving a high “average”.  This solution penalizes hour/month/day combinations where the bridge regularly lifts a few times and isn’t accounting for the majority of occasions in which the bridge lifts ZERO times during the 2pm hour on August Sundays.

Consider the 9 on Saturdays in July combination.  There are a whopping 24 lifts on 2016-07-30, along with a single lift during that window on two other days. 9 on Saturdays in July has a total of 26 lifts in the dataset, more than twice as many times as the provided solution.  The solution suggests that because 12/1 is greater than 26/3, you’re going to be more likely to see the bridge lift on 2pm on August Saturdays.  This doesn’t make sense.

A better solution would be to just find the hour month day combination which occurs the most in the dataset (15 on Saturdays in September occurs 29 times).

The most correct solution probably requires summing the number of lifts during each hour/day/month grouping and dividing by a count of the number of Saturdays, Sundays, etc. in each month during 2015 – 2018.

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