Spreadsheets+5 Swords of Calculation

Fluency with Information Technology

INFO100 and CSE100

Katherine Deibel

2012-02-17 Katherine Deibel, Fluency in Information Technology 1

Katherine Deibel, Fluency in Information Technology 2

Spreadsheets

Powerful tools for managing data Organization

Manipulation

Calculation

Visualization High-level tool for programming

Think of spreadsheets as a handier interface for computing ideas than JavaScript is

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Familiar Terminology

row name

column name

cellformula

column heading

referenced cell L2

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Katherine Deibel, Fluency in Information Technology 4

Similar Metaphors to JavaScript

Variables:Cells are variables (contain data)

Expressions:Setting a cell to a formula is an (unevaluated) assignment statement

Functions and Parameters:Spreadsheets have built-in function

Arrays and IDs:The position (row/column) names the data

Iteration:Operating on all elements in a range as in =SUM(A1:A5)

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Katherine Deibel, Fluency in Information Technology 5

An Array of Cells

A spreadsheet is a 2-D array of cells Multiple sheets make it 3-D

The idea is that the rows or columns represent a common kind of data Adding more data of the same type means

adding more rows or columns

Often spreadsheets contain numbers, but text-only spreadsheets are useful, too

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Clicker Quiz

Let's see what your knowledge of spreadsheet basics is like

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When the $ sign is used in a cell reference, it makes that part of the reference absolute.

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Cell references default to the current sheet.

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Spreadsheets use localization information to determine stylings for things like currency.

In Britain, currency is formatted as £3.33.

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Spreadsheets are clever in how they calculate functions in that they trace dependencies and calculate in the proper order.

Of course, this means that circular references are bad.

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Circular Reference

A B C1 =C1 5 =A1*B1

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Most spreadsheet programs will warn you against circular references and will not get caught in an infinite operation.

Spreadsheets by default show the result of a formula in the row.

You have to click on the cell to see the formula in the edit bar.

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7. A cell cannot contain which of the following?

A. JavaScript code

B. Russian text

C. A URL

D. Date and time

E. Can contain all of the above

Excel cells can contain almost any type of data, JavaScript and Russian included.

What it does with the data, however, may not be what you expect. JavaScript code would be treated as just text.

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Power Use of ExcelMay apply to other spreadsheet programs

Consult your physician before stopping power use of Excel

Offer not valid in Alaska

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Formulas

The data in a spreadsheet can be manipulated using formulas

The value in H2 (selected cell) is the value in F2 times 0.621 … the result is shown, but the cell has the formula

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Apply Formula Again

One way to repeat the formula is to copy-and-paste

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A Powerful Translation

The relative and absolute references work this way because they are in effect:

=[myposition.col -2,myposition.row]*0.621

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Relative vs Absolute Addresses

Reference to cells happens in 2 ways: Relative and Absolute (with $)

F2 relative column, relative row

F$2 relative column, absolute row

$F2 absolute column, relative row

$F$2 absolute column, absolute row

Relative references change when pasted/filled

Absolute references do not change

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An Example

Creating a discount table uses rel and abs refs Consider store credit of $1 per $10 spent

$3 store credit for every 2 CDs (1 earns $1)

=$B3/10 + (3/2)*C$2

=[B,myposition.row]/10 + (3/2)*[myposition.col,2]

B

2

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Filling Replicates Formulas

Fill is a spreadsheet shortcut for copy-and-paste

Grab the fill tab with the cursor and pull in the direction to be pasted

fill tab

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Series

Another handy property of fill is that it can make a series based on constants Fill Sunday => Monday, Tuesday, Wed…

Fill 22 Feb => 23 Feb, 24 Feb, 25 Feb, … More generally

Series fill will even count using a constant

Counting by odd sizes: give 1st two items

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More Advanced Skills

Chapter 15 Case Study – Travel Costs This chapter guides you through

several other power features of Excel Conditional Formatting

Filtering

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Professor Kate's Advanced SkillsCalculations, Formulas, Charts, Etc.

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Mommy plays with Excel instead of me…

Formulas

Spreadsheets come with built-in functions for many purposes: Basic math functions (ABS, FLOOR, EXP)

Statistics (AVERAGE, MEDIAN)

String manipulation (FIND, LEN

Logic (IF, AND, NOT)

And many more

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Formula Help

When you enter a = into the edit bar, you can click on the function button

This brings up a list of functions for you to browse through

Each function also has help files and demos associated with it

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Formula Help

Interactive windows help you fill in formula parameters

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Charts

Visualizations help with communicating large amounts of data Lots of room for flexibility and creativity

Entire course in itself Good place to blaze away and explore Plenty of good tutorials online

One of my favorites is: http://peltiertech.com/

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As A Workspace

Spreadsheets are great because they have lots of cells Spread out your calculations

As they said in elementary school math…

SHOW YOUR WORK!!

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Example

Let's calculate something complex

Yes, Excel has a built-in function for this (STDEV), but let's do this

By the way, μ is the average of the N x's

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Standard Deviation

Summary

Spreadsheets are powerful tools One of the best tools for the digerati

Easy access to programming Spreadsheets are often the easiest

way to make a computer solve your problem if the software for that problem doesn’t already exist

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