# Blog

### Why SUMPRODUCT?

In this article, I attempt to explain why you see SUMPRODUCT so often in formulas, and when you can use the SUM function instead. The short version: SUMPRODUCT supports array operations natively, which makes it very useful for solving seemingly unrelated Excel problems. In the current version of Excel, you can use the SUM instead, but SUMPRODUCT is better for backwards compatibility.

### How to concatenate in Excel

Concatenation is one of the most important operations in more advanced formulas. This article explains how to perform concatenation manually with the ampersand operator (&) and with the three Excel functions designed for concatenation: CONCATENATE, CONCAT, and TEXTJOIN.

### 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 the fastest and easiest way to quickly analyze data 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?