Category Archives: Excel

Computing the Number of Friday the 13ths in a Year Using Excel

Posted on 20-November-2018 by mathscinotes

I have been tutoring math at the local library and using Excel as a vehicle for encouraging people to explore everyday math. While at the library, I heard a young man ask "How many Friday the 13ths are in a year?" Since I am always looking for computational examples, I showed him how to use Excel to find the answer for himself. This post shows how I taught him to solve the problem. The solution turned out to be a good example of using Excel's date and array capabilities. Continue reading →

 
Posted in Excel | 3 Comments

Excel VBA Code to Center a Shape in a Cell

Posted on 17-November-2018 by mathscinotes

I recently finished a job where the customer wanted an Excel dashboard that displayed metrics for test case completion and various success metrics. This dashboard contained many control shapes that I wanted to be centered in cells. I do not like to manually adjust objects so I googled for a VBA routine that would center a shape. I soon found a nice piece of code by HipGecko on the Mr. Excel forum that centered pictures in the active cell. A simple modification of this code allows it to center shapes, an object type that includes pictures and controls. Continue reading →

 
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Using Excel to Compute Effective Tax Rate

Posted on 7-September-2018 by mathscinotes

I have been working as a contractor for the last few months and it is now time for me to make a quarterly tax payment to the folks at the Internal Revenue Service (IRS). This involves using some tables listed on Form 1040ES (see Appendix A). The US tax code uses has a graduated tax rate; the tax rates on higher amounts of income are higher than on lower amounts. As I calculated my tax payment, I became curious as to my effective tax rate. I am going to use Excel to duplicate a graph that I saw on the Wikipedia. My version of the graph is shown in Figure 1. Continue reading →

 
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Using Excel Custom Formatting To Hide Redundant Table Information

Posted on 1-September-2018 by mathscinotes

I currently am doing some contract work as a system engineer. In this role, I am working on generating and managing lists of requirements to drive the engineering design work. The requirements are stored in a database that I query to generate requirements lists for specific subsystems, like a receiver or transmitter assembly. These requirements are disseminated to the engineers in various subsystem documents (Figure 1). Continue reading →

 
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I Forgot – VLOOKUP is Not Case-Sensitive

Posted on 20-July-2018 by mathscinotes

I almost sent out a spreadsheet today that contained a VLOOKUP error – I forgot that VLOOKUP is not case sensitive. Fortunately, I caught my error seconds before I hit send. Today's post is about how I chose to perform a case-sensitive lookup in an ancient version of Excel. Continue reading →

 
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Evenly Spaced Points on Logarithmic Graphic Using Excel

Posted on 9-July-2018 by mathscinotes

I am doing some testing at an Electromagnetic Compatibility (EMC) facility this week. Part of the test specification requires that we inject audio frequency interference on the power supply lines at discrete frequencies that range from 10Hz to 100+KHz, with 30 frequencies selected from each decade of frequencies (e.g. 10 Hz to 100 Hz, 100 Hz to 1 kHz, etc.). Figure 1 shows a specification similar to the one I am performing. My test facility that has chosen the discrete frequencies to be evenly spaced on a logarithmic axis. I started to wonder how the frequencies were selected – let's work through it. Continue reading →

 
Posted in Excel, General Mathematics | 1 Comment

Test Time vs BER and Confidence Level Using Excel

Posted on 4-July-2018 by mathscinotes

I am currently working as a project manager on a serial data channel qualification task. During this work, I need to estimate the time required to perform dozens of Bit Error Rate (BER) measurements under different scenarios (see Figure 1). In these measurements, we are working to ensure that our BER is always 1E-10 or less. I have performed this calculation many times and have derived all the associated formulas here. BER is a statistical parameter and its measurement is a function of the confidence level you want in your answer.  In this case, we want the highest confidence level possible consistent with a two-week test effort. Continue reading →

 
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Computing Dates of Fathers Day with Excel

Posted on 17-June-2018 by mathscinotes

My wedding anniversary (16-June) and Fathers Day are on the same weekend this year. Next year, Fathers Day and my anniversary are on the same day. I became curious about (a) how to compute the date of Fathers Day for each year, and (b) determining the years when Fathers Day and my anniversary occur on the same date. Continue reading →

 
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Liberty Ship Production Data

Posted on 22-May-2018 by mathscinotes

One WW2 battle that we hear little about was fought by logisticians. Their battle was between what could be produced versus what could be delivered in time to matter.  This point was driven home to me when I heard a WW2 historian say that the US had the manufacturing capacity to produce 150K tanks, but that level of tank production would consume all the US steel and leave nothing to build the ships needed to carry the tanks to the fight. Continue reading →

 
Posted in Excel, History Through Spreadsheets, Naval History | 2 Comments

Minnesotans In the Olympics

Posted on 24-February-2018 by mathscinotes

I spend a lot of time in northern Minnesota now that I have a home there. I have been surprised as to how popular curling is in the area (Figure 1). The US curling team at the 2018 Olympics is dominated by people from northern Minnesota. I also notice that there are quite a few Minnesotans participating in the games other sports – the numbers are large enough that the New York Times has even written an article called "Team USA? More Like Team Minnesota" on the topic (PDF of the article). Our state does not have a huge population, ~5 million, and most of that population is concentrated around Minneapolis and St. Paul. The northern part of the state is only sparsely populated as it is covered with national forests and wilderness areas. Continue reading →

 
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