# Blog

### What is an array formula?

In the world of Excel formulas, the term "array formula" is probably responsible for more confusion than just about any other concept. This is because the definition of an array formula has become mixed up with the requirement to enter some array formulas in a special way, with control + shift + enter.

### Excel's RACON functions

There are eight functions in Excel that work differently than you might realize. The same features that were supposed to make them easier to use, can actually make them harder to use :) Read on for important information about COUNTIF, COUNTIFS, SUMIF, SUMIFS,  AVERAGEIF, AVERAGEIFS, MINIFS, and MAXIFS.

This article provides examples of public Coronavirus data you can download to Excel with Power Query. Each example has a link, a screenshot to show what the data looks like in Excel after being imported, and an Excel workbook.

### Tracking COVID-19 with Excel

A quick example of how to track testing for COVID-19 using Excel and publicly available data. In this project, the data is fetched and "shaped" with Power Query, then dropped back into Excel, where it can be refreshed with a single click.

### Alternatives to Dynamic Array Functions

Dynamic Excel offers 6 brand new functions that solve hard problems in Excel like sorting, filtering, and working with unique values. For those not using Office 365, this page provides some alternative formulas that work in older versions of Excel.

### Dynamic array formulas in Excel

Dynamic Arrays are the biggest change to Excel formulas in years. Maybe the biggest change ever. This is because Dynamic Arrays let you easily work with multiple values at the same time in a formula. This article provides an overview with many links and examples.

### Excel Pivot Tables

Pivot tables are one of the most powerful and useful features in Excel. This article is an introduction to Pivot Tables and their benefits, and a step-by-step guide with sample data.

### Excel Formula Errors

Formula errors are useful, because they tell you clearly that something is wrong. This guide shows examples of each of the 9 formula errors you might run into, with information on how to investigate and correct the error.

### How to lookup first and last match

If VLOOKUP finds more than one match, will you get the first match or the last match? It's a trick question. It depends :) This article explains this confusing topic in detail, with lots of examples.

### Excel formulas and functions

Most people never receive proper Excel training and spend years frustrated by the simplest tasks, especially tasks that involve formulas. To use Excel with confidence, you must have a good understanding of formulas and functions. This article introduces the basic concepts you need to know to be proficient with formulas in Excel.

### The double negative in Excel formulas

The double negative coerces TRUE or FALSE values to their numeric equivalents, 1 and 0. This is a useful technique in many advanced formulas that work with cell ranges.

### 101 Excel Functions you should know

Excel contains over 450 functions, with more functions added every year. That is a huge number, so where should you start? This guide provides a walkthrough of over 100 important functions in Excel with many examples and links. Click function names for details and more examples.

### How to use formula criteria (50 examples)

Criteria are a key concept in Excel, but building useful criteria for text, numbers, dates, times, etc. is hard because it requires a good understanding of how Excel handles data. This guide will help you build formulas that work the first time with over 50 examples.

### Excel shows formula but not result

Every once in a while, you might find Excel behaving in a bizarre or unexpected way. One example is when you accidentally trigger the scroll lock feature. Another example is when one or more formulas suddenly stops working. Instead of a result, you see only a formula. What?

### Formula challenge - convert Y/N to days of week

In this challenge, the goal is to end up with a text string like "MWF" for Monday, Wednesday, Friday. The problem is that the weekdays are input like as yes/no abbreviations like "NYNYNYN" for "MWF". What formula will translate the "N" and "Y" to weekday abbreviations?

Every day, thousands of questions about Excel are posted on the internet. Many of these questions go unanswered because they are unclear. This article contains some tips on how to write a question that people will quickly understand and answer if they can.

### Formula challenge - multiple OR criteria

One problem that comes up a lot in Excel is counting or summing based on multiple OR conditions. For example, perhaps you need to analyze data and count orders in Seattle or Denver, for items that are Red, Blue, or Green? This can be surprisingly tricky, so naturally it makes a good challenge!

### Formula challenge - flag out of sequence codes

We have a simple list of 4-digit alphanumeric codes like A001, A002, A003, etc. What formula can we use to mark codes are "out of sequence" with previous entries? This problem includes two separate challenges.

### Formula challenge - 2D lookup and sum

In this formula challenge, we have data showing cups of coffee sold at a small kiosk for a week. What formula will look up and sum total cups sold after 12:00 PM on Tuesday and Thursday? Relevant cells are shaded in green.