How to correct Microsoft Excel's incorrect scatter graphs equation

If you ever had tried to plot a scatter chart in Microsoft Excel and add trend lines and then displayed the equation you sure have found out something weird happening.

The trendline will be correctly plotted but the equation displayed may give you incorrect results if you try to plug and calculate x values manually.

How to solve it?

Let’s see a quick example by plotting the following data set

Plotting Scatter Chart

1. select your data set and plot it by selecting XY scatter diagram and continue pressing the Next tab as appropriate  

2. once you have your graph you can add a trend line to your scattered points,

To do that: click on one of the points and right click and choose Add Trend lines.

Chose which ever type of trend you decide for the curve fitting of your data

Press the Options Tab and check the “Display equation on chart” option

The equation will be displayed and you can select it and can move and place it where ever you want in the chart area

Now if you take this equation (shown on the upper right corner) and plug some X-values it will give you incorrect corresponding y-values.

Microsoft actually says “…..Microsoft Excel plots trendlines correctly. However, the equation that is displayed may give incorrect results when you manually type x values. For appearance, each x value is rounded in the number of significant digits that are displayed in the chart. This behaviour allows the equation to occupy less space in the chart area. However, the accuracy of the chart is significantly reduced, which can cause a trend to appear to be incorrect…..this behaviour is by design”

How to correct it?

1. Select the equation and right click on it and choose Format Data Labeles…

 

2. Press the Number tab and select Number in Category: then set the Decimal places to some larger number say 15,20 or 30 -an amount which will accommodate all your valuable non zero figures

Now you have your correct equation to work with!

                                 

Mathematics, calculus lecture notes

Some web sources for studying calculus (Differential Equations)

Below are some useful links whether you want to study a new calculus course or want to brush up what you have learned before.

Paul's Online Math Notes

I found these notes, which you can download from http://tutorial.math.lamar.edu/ invaluable in revising my calculus lessons. With the easy to understand way of explaining the concepts and clear steps along with witty solved examples, these notes make me ready for a new advanced course almost in no time.

Cramster

With lots of solved exercises from different common college text books, this web site will help you in solving your questions either for homeworks or for practicing. You can have a paid subscription or a free trial at http://www.cramster.com/.

Wolfram alpha

 This is a search engine, which of course can be used for many scholarly applications other than calculus or any math course for that matter. It is so helpful in finding the solution automatically without the hassle and bustle of writing and running different programs. Can check it and explore its interesting features here- http://www.wolframalpha.com/

MIT Opencourseware

 These free online course materials can be downloaded from MIT, they are very useful as most of them are video courses recorded during a real class. You can go to this site http://ocw.mit.edu/index.htm and find the course you are interested in.

Using "Google" other than "search engine"

1.      make conversions

a.       Want to convert feet to meters or vise versa? Just type the value you need to convert, for example 5 feets and hit search or enter. Google calculator will do the conversion automatically.

b.      Want to convert psi into pascals? Just type the value in psi and hit search or enter.

  

2.      Want to know the weather of your city for this winter before you go out or any city? Just write down “weather, Vegas” There you have the data you need in a second.

3.      want to find those “advanced math” values like what is the value of e⁸? shouldn't be hard, Just type e^{^8} and hit search or enter- vola!

4.      Want to know your flight states (US)? Just type the airline and your flight number, there you have it.

         5. ...and to know where and what magnitude the recent earthquake took place on the globe, just type "earthquake" and hit search or enter

You can explore more on this site http://www.google.com/intl/en/help/features.html#calculator