Casio fx-CG 50: Centroid of a 2D spaces

Casio fx-CG 50: Centroid of a 2D spaces

The program CENTROID calculates the center point for an area covered by:

y(x) ≥ 0, x ≥ lower limit, x ≤ upper limit

The center point is calculated by:

x-center = ∫( x * y(x) dx, x = lower limit, x = upper limit) / A

y-center = ∫(1 / 2 * y(x)^2 dx, x = lower limit, x = upper limit) / A

where A = ∫( y(x) dx, x = lower limit, x = upper limit)

Casio fx-CG 50 Program Code: CENTROID

Here is the code, which includes a graphic representation of y(x) and the location of the centroid. In this code, the Y is bold and it comes from the VARS menu. Do not merely use ALPHA+Y. For calculators with monochrome screens, such as the fx-9750G/fx-9860G series, leave out the color commands (Black, Blue, Red). The program assumes that there no preset plots or more than one function to be plotted.

This program works best for functions y(x) ≥ 0 for x ∈ [lower limit, upper limit].

Here is a text-only version:

Examples

Example 1: y = x^2 , lower limit = 0, upper limit = 1

X-Center = 3 / 4 = 0.75

Y-Center = 3 / 10 = 0.3

Example 2: y = 2 * cos( x / 2 ), lower limit = 0, upper limit = π

X-Center ≈ 1.141592654

Y-Center ≈ 0.7853981634

Example 3: y = 3, lower limit = 1, upper limit = 5

X-Center = 3

Y-Center = 1.5

Example 4: y = -4 * x^2 + 2 * x + 6, lower limit = -0.5, upper limit = 1

X-Center = 1 / 4

Y-Center = 307 / 110

Eddie

All original content copyright, © 2011-2024. Edward Shore. Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited. This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author.

Sum of Sequential Integers (featuring Swiss Micros DM32)

 Sum of Sequential Integers (featuring Swiss Micros DM32)

What is the sum of the following:

100 + 101 + 102 + 103 + 104 + 105 + … + 997 + 998 + 999?

It’s doable on a calculator, but going straight forward will require a lot of keystrokes (unless you have access to the sigma function (Σ)).

Note that:

100 + 101 + 102 + 103 + 104 + 105 + … + 997 + 998 + 999

= 100 + (100 + 1) + (100 + 2) + (100 + 3) + (100 + 4) + …. + (100 + 897) + (100 + 898) + (100 + 899)

= (100 + 0) + (100 + 1) + (100 + 2) + (100 + 3) + (100 + 4) + …. + (100 + 897) + (100 + 898) + (100 + 899)

Notice the sum starts with a base, 100. The sequence goes for 900 terms in the form of 100+n where n = 0 to 899. Let’s look at a general case.

Let x be a base integer, and S be the sum as:

S = (x + 0) + (x + 1) + (x + 2) + (x + 3) + …. + (x + n)

Rearranging the terms leads us to:

S = (x + x + x + x + … + x) + (0 + 1 + 2 + 3 + 4 + … + n)

There are n + 1 pairs:

S = (x * (n + 1)) + (0 + 1 + 2 + 3 + 4 + … + n)

S = (x * (n + 1)) + (1 + 2 + 3 + 4 + … + n)

The sum of Σ( k, k = 1 to k = n) = 1 + 2 + 3 + 4 + … + n = n * (n + 1) / 2

Then:

S = (x * (n + 1)) + n * (n + 1) / 2

Let’s look at some specific examples:

n = 1

S = (x + 0) + (x + 1)

S = (x + x) + (0 +1)

S = 2 * x + 1

n = 2

S = (x + 0) + (x + 1) + (x + 2)

S = (x + x + x) + (0 + 1 + 2)

S = 3 * x + 3

2 * 3 / 2 = 3

n = 3

S = (x + 0) + (x + 1) + (x + 2) + (x + 3)

S = (x + x + x + x) + (0 + 1 + 2 + 3)

S = 4 * x + 6

3 * 4 / 2 = 6

S = 500 + 501 +502 + 503

S = (500 + 0) + (500 + 1) + (500 + 2) + (500 + 3)

S = (500 + 500 + 500 + 500) + (0 + 1 + 2 + 3)

S = ((3 + 1) * 500) + (3 * 4 / 2)

S = 2000 + 6

S = 2006

S = 250 + 251 + 252 + 253 + … + 269 + 270

Base = 250

n = 270 – 250 = 20

Then:

S = 250 * (20 + 1) + 20 * 21 / 2

S = 5460

Let’s go our original problem:

S = 100 + 101 + 102 + 103 + 104 + 105 + … + 997 + 998 + 999

Base = 100

n = 999 -100 = 899

Then:

S = 100 * (899 + 1) + 899 * 900 / 2

S = 90000 + 404550

S = 494550

The program code calculates the sum:

Swiss Micros DM32 Program (also HP 32SII)

S01 LBL S

S02 INPUT X

S03 INPUT N

S04 RCL N

S05 1

S06 +

S07 RCL× N

S08 RCL N

S09 1

S10 RCL+ N

S11 ×

S12 2

S13 ÷

S14 +

S15 RTN

Eddie

All original content copyright, © 2011-2024. Edward Shore. Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited. This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author.

TI-30Xa Algorithm: Synthetic Division

TI-30Xa Algorithm:  Synthetic Division

Introduction

Synthetic division is a fairly simple division algorithm that divides a polynomial by the nominal (x-a):

p(x) / (x  - c) where

p(x) = a_n * x^n + a_n-1 * x^(n-1) + a_n-2 * x^(n - 2) + … + a_1 * x + a_0

c = a numerical constant

the result, q(x), is a polynomial of order n-1:

q(x) = b_n-1 * x^(n-1) + b_n-2 * x^(n - 2) + … + b_1 * x + b_0 + b_r / (x - c)

b_r = remainder term

where 

b_n-1 = a_n

b_i-1 = b_i  * c + a_i for i = n-2 down to r (“-1”, see the example below)  

For example, for the polynomial:

p(x) = a3 * x^3 + a2 * x^2 + a1 * x + a0

q(x) = p(x) / (x - c) 

p(x) has the order n = 3, so q(x) will have the order n = 3 - 1 = 2:

q(x) = b2 * x^2 + b1 * x + b0 + br / (x - c)

b2 = a3

b1 = b2 * c + a2

b0 = b1 * c + a1

br = b0 * c + a0  (the algorithm stops, this is the remainder term)

If br = 0, the x - c divides p(x) evenly, and x = c is a root of p(x).  

Note: for any “missing” terms, fill the term with 0.   

Example:  x^3 + 4 * x - 5 becomes x^3 + 0 * x^2 + 4 * x - 5.

Calculator Algorithm

1. Store c in one of the memory registers 1, 2, or 3.   We’ll call this memory register m for the purpose of the blog.

2. Note the first coefficient of q(x):  a_n

3. Compute the rest of the coefficients as follows:  [ × ] [ RCL ] m [ + ] a_ni [ = ]

Examples

Remember:  m is memory register 1, 2, or 3, your choice.  

Example 1:  (21 * x^2 + 42 * x + 144) / (x - 12) 

c = 12

a2 = 21

a1 = 42

a0 = 144

b1 = a2 = 21

12 [ STO ] m

Enter 21

b0:

[ × ] [ RCL ] m [ + ] 42 [ = ]

Result:  294

br:

[ × ] [ RCL ] m [ + ] 144 [ = ]

Result:  3672

Stop.

q(x) = 21 * x + 294 + 3672 / (x - 12)

Example 2:  (2 * x^3 + x - 3) / (x - 3) = (2 * x^3 + 0 * x^2 + x - 3) / (x - 3)

c = 3

a3 = 2

a2 = 0

a1 = 1

a0 = -3

b2 = a3 = 2

3 [ STO ] m

Enter 2

b1:

[ × ] [ RCL ] m [ + ] 0 [ = ]

Result:  6

b0:

[ × ] [ RCL ] m [ + ] 1 [ = ]

Result:  19

br:

[ × ] [ RCL ] m [ + ] 3 [ +/- ]  [ = ]

Result:  54

q(x) = 2 * x^2 + 6 * x + 19 + 54 / (x - 3)

Example 3:  (4 * x^3 + 8 * x^2 - 5 * x + 3) / (x + 2)

c = -2

a3 = 4

a2 = 8

a1 = -5

a0 = 3

b2 = a3 = 4

2 [ +/- ] [ STO ] m 

Enter 4

b2:

[ × ] [ RCL ] m [ + ] 8 [ = ]

Result:  0

b3:

[ × ] [ RCL ] m [ + ] 5 [+/-] [ = ]

Result:  -5

br:

[ × ] [ RCL ] m [ + ] 3 [ = ]

Result:  13

q(x) = 4 * x^2 - 5 + 13 / (x + 2)

I think this is a fundamental algorithm for students and math enthusiasts to learn, and it’s fairly simple to get a hang of it. 

Until next time,

Eddie

Quick update: Starting October 5, 2024, my schedule will allow me to blog once a week. Regular posts will go live every Saturday. Thank you for your support and compliments. I wish you all well.

All original content copyright, © 2011-2024. Edward Shore. Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited. This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author.

  

TI-84 CE and TI-86: Matrix Row Statistics

TI-84 CE and TI-86: Matrix Row Statistics

Introduction

The program MROWST will take a matrix and a desired row and calculate three statistics points:

* Sum of the row

* Mean of the row

* Difference Vector: row – mean for each element

TI-84 CE Program MROWST

Matrices used: [ J ] (entry matrix), [ I ] (difference vector)

Input “MATRIX? “, [ J ]

Input “ROW? “, R

dim([ J ])

Ans(2) → D

0 → S

For(I, 1, D)

S + [ J ](R, I) → S

End

S / D → M

{1, D} → dim([ I ])

For(I, 1, D)

[ J ](R, I) – M → [ I ](1, I)

End

ClrHome

Disp “SUM: “ + toString(S)

Disp “MEAN: “ + toString(M)

Disp “DIFF VECTOR:”

Pause [ I ]

TI-86 Program MROWST

Matrices used: MJ (entry matrix), MD (difference vector), mone (vector of ones)

Input “Matrix? “, MJ

Input “Row? “, R

dim MJ

Ans(2) → D

D → dim mone

Fill(1, mone)

dot(mone, MJ(R)) → S

S / dim mone → M

MJ(R) - (M * mone) → MD

ClLCD

Disp “Sum:”, S

Disp “Mean:”, M

Disp “Diff Vector:”

Pause MD

Example

Matrix:

[ [ -9, -4, -1, -9, 4 ]

[ -9, -7, -4, -4, 9 ]

[ 7, 1, -9, -7, 8 ] ]

Row 1:

Sum: -1

Mean: -0.2

Difference Vector: [ 9.2, -3.8, -0.8, -8.8, 4.2 ]

Row 2:

Sum: -15

Mean: -3

Difference Vector: [ -6, -4, -1, -1, 12 ]

Row 3:

Sum: 0

Mean: 0

Difference Vector: [ 7, 1, -9, -7, 8 ]

Source:

Stuerke, Cecil. “Demonstration of Principal Component Analysis on TI-86” IEEE 2008

Eddie

Quick update: Starting October 5, 2024, my schedule will allow me to blog once a week. Regular posts will go live every Saturday. Thank you for your support and compliments. I wish you all well.

All original content copyright, © 2011-2024. Edward Shore. Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited. This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author.

Numworks: Allowing Repeated Calculations in Python

Numworks: Allowing Repeated Calculations in Python

Introduction

Say we want the user to repeat a calculation or a routine for as long as the user wants. At the end of each calculation, the user is asked if they want another calculation. The user enters one of two possibilities:

1 for an additional calculation

0 for no more calculation

A flag variable is set up with a default value of 1. As long as this value remains at 1, the calculation repeats.

Scrip structure (I named this variable rptflag, but it can be any name):

rptflag=1

while rptflag!=0:

  …

  < insert inputs and show results >

  …

  print(“Again? No = 0, Yes = 1”)

  rptflag=eval(input())

Entering 0 for the Again? Question exits the loop. We need the eval (evaluate) or int (input) because leaving the input command alone defaults the input to a string.

For the sample scripts below, the escape velocity off the surface of planets and other celestial objects are calculated.

Repeated Loop: General

This script does not require any special modules.

Script: rptdemo1 (We can use this on any calculator or platform)

from math import *

# repeat demonstration 

# set up repeat flag

rptflag=1

while rptflag!=0:

  print("ESCAPE VELOCITY")

  m=eval(input("Mass (kg)? "))

  r=eval(input("Radius (m)? "))

  v=sqrt(1.33486e-10*m/r)

  print("Velocity: ",v,"\nm/s")

  print("Again? no=0, 1=yes")

  rptflag=eval(input())

Repeated Loop: Numworks – using the keyboard

Instead of having the user enter 0 or 1, the user presses the keys 0 or 1. To allow the user key presses, use the Ion module. KEY_ZERO is for the 0 key and KEY_ONE is for the 1 key.

To make the screen look presentable, I’m clearing the screen. This is accomplished by the use of the Kandinsky module. The use of the Kandinsky module was suggest to me on Reddit by Feeling_Walrus3033, and I give credit and gratitude for the suggestion.

The line:

fill_rect(0,0,320,240,(255,255,255)) creates a blank white screen.

Clearing the screen this way will call for a way to display text on the screen. Unfortunately the print() command won’t do it. Kandinsky comes to the rescue with the draw_string command. The syntax for the draw_string command is:

draw_string(“text” or variable containing the string, x pixel, y pixel, [text color], [background color])

Colors are optional. The default is black text on white background.

Keep in mind that using this method will require more memory.

Script: rptdemo2 (Specific to Numworks, for other platforms and calculator, check your specific manual)

from math import *

from ion import *

from kandinsky import *

# repeat demonstration 

# set up keys

def key():

  while True:

    if keydown(KEY_ZERO):

      return 0

    if keydown(KEY_ONE):

      return 1

# set up repeat flag

rptflag=1

while rptflag==1:

  print("ESCAPE VELOCITY")

  m=eval(input("Mass (kg)? "))

  r=eval(input("Radius (m)? "))

  v=sqrt(1.33486e-10*m/r)

  

  # build strings

  s1="Velocity: "+str(v)+" m/s"

  s2="Again? no=0, 1=yes"

  fill_rect(0,0,320,240,(255,255,255))

  draw_string(s1,0,0)

  draw_string(s2,0,20)

  rptflag=key()

draw_string("DONE",0,40,(255,0,0))

Sample Data to Try

	Mass (kg)	Radius (m)	Escape Velocity (m/s)
Earth	5.972168E24	6378.137E3	11179.88618486758
Jupiter	1.8982E27	71492E3	59533.32250562
Sun (Solar System)	1.9885E30	6.957E8	617688.6988877566

E: [ ×10^x ] button, shown as “e”

Note: I will be in Nashville for the 2024 HP Handheld Conference on September 21-22, 2024. The next scheduled post will be on September 28, 2024.

Take care,

Eddie

All original content copyright, © 2011-2024. Edward Shore. Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited. This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author.