TI-84 Plus (and General Graphing): Semi Log Plots (LINLOG)
Introduction
Many
applications, such as the Bode Plot, are plotted as a semi-log plot. In particular, a lin log plot is used. In a
lin log plot, the x-axis is on a logarithmic scale, while the y-axis is a
linear scale.
 |
| Lin Log Grid |
Graphing
calculators do not have a lin log plot mode (at least not that I know of). However, we can simulate lin log plots.
How to Simulate Lin Log
Plots
We are going to
enter Function plotting mode (y(x)) as usual.
The trick here is to substitute every x with 10^x or ALOG(x). For example:
y(x) = 5*x – 2 becomes
y(x)
= 5 * 10^x – 2 or y(x) = 5 * ALOG(x) – 2
In essence, we
think of the x axis not as {0, 1, 2, 3, …} but {10^0, 10^1, 10^2, 10^3, ….
}.
Caution: With certain functions, the range can grow
quickly. Be careful on how you set the
axis.
Reference: 10^0 = 1, 10^1 = 10, 10^2 = 100, 10^3 = 1,000
The TI-84 Plus
program LINLOG uses a list plot of a function and sets the axis to the
appropriate settings.
TI-84 Plus Program LINLOG
PlotsOff
FnOff
Disp
"LOGARITHMIC X AXIS"
Disp
"10^{0,1,2,...,N}"
Disp "USE
QUOTES"
Input "Y =
",Y₁
Input "TO 10^N:
",N
{0}→L1
10^(0)→X
{Y1}→L2
For(I,0,N,0.1)
10^(I)→X
augment(L1,{I})→L1
augment(L2,{Y1})→L2
End
Plot1(xyLine,L1,L2)
ZoomStat
Be sure to use
quotations when entering the function.
Remember that X in this case represents 10^x. Below are example plots.
 |
| y = x / 2 |
 |
| y = log x |
Try it, I hope
you find this helpful. Thank you for
your support and comments. See you next
time,
Eddie
This blog is
property of Edward Shore, 2017