The content of this blog is just based on my own experience, which means it could be somewhat subjective. The main reason that I take the program is just because I want to consolidate and polish some knowledge in the data engineering field.

Photo by SELİM ARDA ERYILMAZ on Unsplash

The Data Engineering Nanodegree program has five core pillars: Data Modelling, Cloud Data Warehouses, Data Lakes with Spark, Data Pipelines with Airflow, and the Capstone Project. The upcoming content will cover all of these pillars, respectively. In the end, I will express my view about it.

Data Modelling

This module mainly introduces the concept of data modeling in…

Photo by NIO


Followed by its great earnings in Q3, NIO continuously providing a series of amazing results for its Q4 earnings:

  • Total Revenues reached RMB6,641.1 M ($1,017.8 M).
  • Vehicle Sales were RMB6,174.0 M ($946.2 M) with 17,353 total number cars delivered (7,574 ES6, 4,873 ES8, and 4,906 EC6), and the vehicle margin was 17.2%
  • Net loss was RMB 1,388.6 M ($212.8 M), which was decreased by 51.5% from 2019Q4 and an increase of 32.6% of 2020Q3.
  • Cash and cash equivalents, restricted cash, and short-term investment were RMB42.5 B ($6.5 B).
  • The monthly production capacity has reached 7,500 units per month in 2021.

Photo by Macau Photo Agency on Unsplash


Followed by its surprising earnings in Q2, NIO continues providing a series of amazing results for its Q3 earnings:

  • Total Revenues reached RMB4,526.0 M ($666.6 M).
  • Vehicle Sales were RMB4,266.8 M ($628.4 M) with 12,206 total number of cars delivered (8,660 ES6, 3530 ES8, and 16 EC6).
  • Vehicle margin was 14.5%, ES8 contributed a lot in this portion.
  • Net loss was RMB 1,047.0 M ($154.2 M), which was decreased by 58% from 2019Q3 and 11% from 2020Q2.
  • Cash and cash equivalents, restricted cash, and short-term investment were RMB22.2 B ($3.3 …

The cover page from Jesse Livermore — Boy Plunger: The Man Who Sold America Short in 1929

Reminiscences of a Stock Operator is a roman à clef written by Edwin Lefèvre. The whole book describes the life of the legendary stock speculator Jesse Livermore (Larry Livermore in this novel). I will summarise the book and share some of my reactions in a couple of blogs.

The Fledgling

I was most interested in verifying whether I had observed accurately; in other words, whether I was right.

I think this is a very unique motivation for a kid who was only about 14 and started trading — most adults don’t even have such vision — people usually only trade for making…

Photo by NIO


NIO just released its Q2 earnings report and had the earnings call, and I will list some crucial information about this call below.

In the beginning, William gave the opening remarks below:

  • NIO will increase budget in autonomous driving in R&D;
  • The number of preorders of EC6 beyond the internal prediction (no detailed numbers got disclosed);
  • The production line has started to increase the production capacity from 15 jobs per hour (JPH) to 20 JPH and it will reach from 4500 to 5000 production capacity by the end of August;
  • The announcement of Battery as a Service (BaaS) has been…

Graph by Hadley Wickham in Advanced R

This post will share my experience about how to measure the performance of code in R. As an R programmer, you may have heard

apply() functions are usually more efficient than for-loops.

However, you may ask that how can we measure this efficiency and how can we quantify the performance of our functions?

One of the most direct ways to know how long your code runs is using system.time():

From the above results, the elapsed time to run function for_fun is 0.13 seconds. However, to some extent, using system.time()

Renzhi He

Data Engineer. Interested in topics related to data engineering, marketing, and investment in general.

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