Excel: How to make a graph from data and get an equation, 4 easy steps

The tutor shares quick, easy way to get a graph and equation from Excel, 2007 version.

  1. Let’s imagine your x data is in range a1:a10, your y-data, b1:b10.
  2. Select a1:b10, then click Insert, then the Scatter icon. Then, in the drop-down that appears, click the one that looks like a scatter plot. Hopefully you’ll see your chart.
  3. Now, from the toolbar across the top, click Layout. A Trendline icon should appear; click it. You’ll see some choices, along with a More Trendline Options choice. If you want to see the equation on the graph, you must select More Trendline Options.
  4. Select the type of equation you want. Then, near the bottom, notice a check-box: Display Equation on chart. You must check that to see the equation on the chart.

HTH:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Calculator Usage: changing the cells of the TI-30XA

The tutor shares a bit of calculator maintenance.

The TI-30XA uses two cells. The ones I took out of mine say GPA76. I replaced them with AG13 cells; the calculator seems to work fine.

The back of the TI-30XA has six screws. Unfastening them all, it comes apart and the cells are easy to see and change.

HTH:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Spreadsheets: regression curves: power vs exponential

The tutor explains the difference between power and exponential curves.

According to Excel, a power equation has the form

y=axb

whereas an exponential equation has the form

y=aekx

Example:

I tried both options on the following data:

x y
0.5 0.9
1 2.9
3 10.1
4 18.7
5 40

Excel gave me the following regression equations:

Power: y=2.5804x1.514

Exponential: y=0.902e0.7707x

To my observation, Excel will not offer a power equation if x=0 is in the data. It will not offer an exponential if (0,0) is in the data.

I’ll be telling how to get an equation for a given data set in future posts:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Spreadsheets: Excel: the logest() function

The tutor shows how to use the logest() function to get an exponential curve from data.

Excel’s logest() function returns parameters for the equation y=bm^x, according to data fed for x and y values. Let’s imagine the data is as follows:

x y
0 3
1 5
3 16
4 27
5 61

Here’s how to get the parameters for the y=bm^x equation to fit the data:

  1. Let’s imagine the x-data is in range a1:a5; the y-data, b1:b5.
  2. Go to a cell somewhere else, then select it and drag to the one next door, so that both cells are selected.
  3. Key in =logest(b1:b5,a1:a5) but don’t hit enter!
  4. Now, press Ctrl+Shift+Enter (all at once).
  5. Hopefully, you receive two entries: 1.805018 and 2.834844
  6. The form of the equation is y=2.834844*1.805018^x

HTH:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Spreadsheets: linear regression in four easy steps on Excel or LibreOffice Calc

The tutor shows how to get a best-fit line using Excel or LibreOffice Calc.

Let’s imagine you want a best fit line of form y=mx + b for the following data:

x y
0 3
2 5
6 10
8 12

With Excel or LibreOfficeCalc, you do exactly the same steps:

  1. Enter the data in two columns. Let’s imagine the x data is in a1:a4, the y, b1:b4.
  2. In a different cell, key in =slope(b1:b4,a1:a4). Note that the y range is entered first. The answer that appears is the slope of the line, or m. Hopefully, in this case, you get 1.15.
  3. In another cell, key in =intercept(b1:b4,a1:a4). The answer returned is the y intercept, or b; in this case, it’s hopefully 2.9.
  4. For this data, the best-fit line is y=1.15x + 2.9

HTH:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Web design: z-index: one way to superpose content

The tutor shows a way to place content over other content.

To put content on top of other content, the z-index style parameter can be used. If two elements are set at the same absolute position, the one with the higher z-index will display in front.

In the demo here, How are you? has z-index 3, while Hello;) has z-index 1.

Source:

w3schools

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Web Programming: JavaScript: how to manage a multi-line string

The tutor tells a trick for printing long strings with JavaScript.

Suppose you have a long string, over many lines, that you want to print with JavaScript.

Typically, to print a string, you might assign it to a variable, then print the variable:

var string_0=”Getting ready for Christmas…(and so on)…”;
document.getElementById(“div_0”).innerHTML=string_0;

In my experience, if the program you’re using puts a line break in the string, that seems okay. However, JavaScript may not allow an explicit line break in a string variable:

var string_0=”Getting
ready
for
Christmas”; seems not to work

Nonetheless,

var string_0=”Getting “+
“ready “+
“for “+
“Christmas….”;

will print as

That’s what I’ve noticed, anyhow:)

Source:

w3schools

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Web design: a JavaScript wrapper for SVG in WordPress

The tutor shows an example of a wrapper program in action.

To my knowledge, a wrapper is a program that hides a function that the managing system can’t handle. The “wrapping” is code that the managing system recognizes as the responsibility of another service, which it calls. The called service then executes the code inside the “wrapping”.

Here’s a example: SVG in WordPress. I’ve never gotten SVG to work in WordPress. (I’ve heard there are plugins for it, but haven’t tried any.) Yet, SVG is supported by the browser. I asked, “Could I embed SVG in JavaScript, which WordPress will turn over to the browser?”

Looking at the graphic above, the answer seems to be “yes”. The JavaScript wrapper program works: it allows SVG to be executed onto a WordPress page, when WordPress itself (to my knowledge) won’t do so without a plugin.

Source:

jenkov.com
Mozilla Foundation
w3schools.com
stackexchange.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Linear algebra: matrix multiplication: no cancellation rule

The tutor gives an example to show that with matrices, AB=AC doesn’t mean B=C.

Consider the matrices A, B, C, and D:

By matrix multiplication, AB=AC. (In fact, both products equal D.) Yet, obviously, B≠C. Matrix multiplication lacks the cancellation law that you see with the real numbers.

HTH:)

Source:

Johnson/Riess/Arnold. Introduction to Linear Algebra. Don Mills: Addison-Wesley, 1989.

Calculus: concavity and point of inflection

The tutor explains concavity and point of inflection with an example.


Concavity refers to an aspect of graph shape. My first-year calculus professor explained it this way: concave upward will collect rain, while concave downward will shed rain. Numerically, when the second derivative is positive, the graph is concave upward. When the second derivative is negative, the graph is concave downward.

In the graph above, the section from P to Q is concave downward; from Q to R is concave upward.

A point where concavity changes from negative to positive (or positive to negative) is called a point of inflection. In the graph above, Points Q and R are inflection points.

At a point of inflection, the second derivative is either 0 or undefined. However, f”=0 doesn’t guarantee a point of inflection; you still have to check either side (if you can’t see the graph).

The graph above, y=sinx, has second derivative -sinx. At point Q (where x=Π), -sin(Π)=0. Just to the left, -sin3=-0.1411. (Recall Π=3.14159….) Past Π, -sin3.3=0.1577. The sign change across Π confirms the inflection point at (Π,0).

Source:

Larson, Roland and Robert Hostetler. Calculus, part one. Toronto: D C Heath and Company, 1989.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.