Author Archives: Henry

Another Quadratic Programming Example with R

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Following Quadratic Programming with R, this is another example of how to solve quadratic programming problem with R package “quadprog“.

Why Another Example?

Quadratic programming matrix math notation
quadratic programming matrix notation

“quadprog” package requires us to rewrite the quadratic equation in the proper matrix equation as above. You may have the following questions:

  • What if our equation is to maximize the objective function instead of minimize it?
  • What if the inequality constraints are “less than (<=)” instead of “more than (>=)”?
  • What if there is no equality constraints?
  • …

To give you an idea how to answer these questions, this post will give you another example.

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Marketing Analytics with R – Google Search Console

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I have been exploring a couple of marketing platforms in my new job as a Marketing Analyst. One of the daily jobs which I like most is to use R to dig into data across different marketing channels to come up with new ideas and recommendations for our marketing activities.

Google Search Console

Google Search Console is one of the platforms I have been playing with recently. As you may already know, Google Search Console is a useful website tool for marketers to check website overall performance (e.g., search engine crawl and index issues, google search performance). For example, here is the performance report for my personal blog:

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ROC Curve Simulation – Classification Performance

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“A receiver operating characteristic curve, or ROC curve, is a graphical plot that illustrates the diagnostic ability of a binary classifier system as its discrimination threshold is varied. The ROC curve is created by plotting the true positive rate against the false positive rate at various threshold settings.” – Wikipedia

Simulation can be very useful for us to understand some concepts in Statistics, as shown in Probability in R. Here is another example that I used simulation to understand ROC Curve and AUC, the metrics in classification models that I had never fully understand.

Data

The simulation in this post was inspired by OpenIntro Statistics and the email dataset I used can be found in openintro package.

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R Markdown to WordPress with goodpress

I have been writing a few posts about R on my blog and are getting annoyed with the workflow back and forth between RStudio and WordPress. Overall, the previous workflow has two main pitfalls making me frustrated:

  • R Code

Coping R code from RStudio and pasting it to WordPress can take me much time. Code highlight is also challenging, although eventually I figured out that the plugin of SyntaxHighlighter Evolved did a great job.

  • R Output

Often I need to export R outputs (e.g., ggplot2 plots) and upload them to WordPress, sometimes formatting them a bit.

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Learning ggplot2 on Paper – Scale

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The previous two posts in this series of learning ggplot2 on paper:

This post will continue to discuss another ggplot2 component, Scale. Let’s start with the graphs we drew in the last post of “Learning ggplot2 on Paper – Layer“, as shown here.

Figure 1
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