Ploting x=constant
05-15-2022, 07:23 PM
Post: #1
 John P Member Posts: 206 Joined: Dec 2013
Ploting x=constant
Hello,
How do I plot on HP Prime for example x=1?
Thank you.
05-15-2022, 07:38 PM
Post: #2
 Eddie W. Shore Senior Member Posts: 1,358 Joined: Dec 2013
RE: Ploting x=constant
This is probably the easiest way to do it:

Symb View: V1: X = 1
05-15-2022, 07:44 PM
Post: #3
 John P Member Posts: 206 Joined: Dec 2013
RE: Ploting x=constant
(05-15-2022 07:38 PM)Eddie W. Shore Wrote:  This is probably the easiest way to do it:

Symb View: V1: X = 1

Thanks. Do you know how to do it in Function Application?
05-15-2022, 07:50 PM
Post: #4
 Eddie W. Shore Senior Member Posts: 1,358 Joined: Dec 2013
RE: Ploting x=constant
Technically x=1 is not a function, hence, it won't fit the y(x) definition.

No, and I don't think there is a vertical draw function to draw x=1 in function. We have LINE, however, that is between two points.

Another way to draw is to use the Parametric app:
X1(T) = 1
Y1(T) = T
set T for any interval you like (but it is finite)
05-15-2022, 07:52 PM
Post: #5
 matalog Member Posts: 206 Joined: May 2021
RE: Ploting x=constant
I was trying to do this the other day too, basically plot a vertical line in Function graphing app.

I'm not sure you can, as it doesn't seem to allow one graph to have 2 points at the same x value, you are plotting F(x) which is basically Y=, is what I concluded.

I hope I am wrong, and there is a way to do it.
05-15-2022, 07:53 PM
Post: #6
 John P Member Posts: 206 Joined: Dec 2013
RE: Ploting x=constant
(05-15-2022 07:50 PM)Eddie W. Shore Wrote:  Technically x=1 is not a function, hence, it won't fit the y(x) definition.

No, and I don't think there is a vertical draw function to draw x=1 in function. We have LINE, however, that is between two points.

Another way to draw is to use the Parametric app:
X1(T) = 1
Y1(T) = T
set T for any interval you like (but it is finite)

Thank you very much.
05-15-2022, 07:57 PM
Post: #7
 John P Member Posts: 206 Joined: Dec 2013
RE: Ploting x=constant
(05-15-2022 07:52 PM)matalog Wrote:  I was trying to do this the other day too, basically plot a vertical line in Function graphing app.

I'm not sure you can, as it doesn't seem to allow one graph to have 2 points at the same x value, you are plotting F(x) which is basically Y=, is what I concluded.

I hope I am wrong, and there is a way to do it.

Hello,
I did not use HP Prime for some time. I was using Pocket CAS on my iPhone. In Pocket Ca you just enter for example x=1, and it is done.
05-15-2022, 08:59 PM
Post: #8
 Didier Lachieze Senior Member Posts: 1,508 Joined: Dec 2013
RE: Ploting x=constant
(05-15-2022 07:52 PM)matalog Wrote:  I was trying to do this the other day too, basically plot a vertical line in Function graphing app.

I'm not sure you can, as it doesn't seem to allow one graph to have 2 points at the same x value, you are plotting F(x) which is basically Y=, is what I concluded.

I hope I am wrong, and there is a way to do it.

You can get a good approximation with something like F1(X)=1E20*(X-1) which will plot a quasi-vertical line at X=1 in the Function app.
05-16-2022, 01:00 AM
Post: #9
 John P Member Posts: 206 Joined: Dec 2013
RE: Ploting x=constant
Hello,
Just suggestion for plotting constants on HP Prime in Function Application.
I do not know if that is possible, but why not introduce in function definition the “WHERE” option, eg. F1(X)=X|(X=const) and plot the vertical line at X=const. Just thinking.
05-19-2022, 11:52 PM
Post: #10
 jte Member Posts: 165 Joined: Feb 2014
RE: Ploting x=constant
(05-16-2022 01:00 AM)John P Wrote:
Just suggestion for plotting constants on HP Prime in Function Application.
I do not know if that is possible, but why not introduce in function definition the “WHERE” option, eg. F1(X)=X|(X=const) and plot the vertical line at X=const. Just thinking.

“WHERE” can currently be used in the Function app; F1(X)=(K+COS(K))|(K=2), for example, will plot as F1(X)=2+COS(2). (That said, how the Function app deals with “|(X=…)” in definitions of functions to be plotted should be adjusted.)

Being able to switch the independent variable for some of the functions could allow one to plot, e.g., F1(Y)=const, but would also require changes in other places (such as the Numeric view, but also the Fcn choices in Plot views). This could become a bit of a can of worms… (And, from a certain viewpoint, the ”X” is a placeholder in F1(X) — it is, simply, the name of the variable to be used in the definition, and the Plot view works with functions from R to R [the name ”X” is bound within the definition and not visible from outside the definition].)

Perhaps some tick customization options could get you what you want: being able to add specific X values to a list (in Plot Setup) that would then be dashed lines in plot views. Comments?
05-20-2022, 12:00 AM
Post: #11
 jte Member Posts: 165 Joined: Feb 2014
RE: Ploting x=constant
(05-15-2022 08:59 PM)Didier Lachieze Wrote:
(05-15-2022 07:52 PM)matalog Wrote:  I was trying to do this the other day too, basically plot a vertical line in Function graphing app.

I’m not sure you can, as it doesn’t seem to allow one graph to have 2 points at the same x value, you are plotting F(x) which is basically Y=, is what I concluded.

I hope I am wrong, and there is a way to do it.

You can get a good approximation with something like F1(X)=1E20*(X-1) which will plot a quasi-vertical line at X=1 in the Function app.

One approach along these lines would be to add a continuous step function (like Heaviside, but known to be continuous and with the transition from 0 to 1 made in the gap between adjacent floating-point numbers). Such a function could then be scaled and shifted to produce other sorts of (continuous) steps.
05-20-2022, 12:06 AM
Post: #12
 jte Member Posts: 165 Joined: Feb 2014
RE: Ploting x=constant
(05-15-2022 07:52 PM)matalog Wrote:  I was trying to do this the other day too, basically plot a vertical line in Function graphing app.

I’m not sure you can, as it doesn’t seem to allow one graph to have 2 points at the same x value, you are plotting F(x) which is basically Y=, is what I concluded.

I hope I am wrong, and there is a way to do it.

Options that come to mind for me follow the paths set out nicely by others in this thread (and I am the one who implemented the Function app…).
05-20-2022, 03:31 AM
Post: #13
 John P Member Posts: 206 Joined: Dec 2013
RE: Ploting x=constant
(05-19-2022 11:52 PM)jte Wrote:
(05-16-2022 01:00 AM)John P Wrote:
Just suggestion for plotting constants on HP Prime in Function Application.
I do not know if that is possible, but why not introduce in function definition the “WHERE” option, eg. F1(X)=X|(X=const) and plot the vertical line at X=const. Just thinking.

“WHERE” can currently be used in the Function app; F1(X)=(K+COS(K))|(K=2), for example, will plot as F1(X)=2+COS(2). (That said, how the Function app deals with “|(X=…)” in definitions of functions to be plotted should be adjusted.)

Being able to switch the independent variable for some of the functions could allow one to plot, e.g., F1(Y)=const, but would also require changes in other places (such as the Numeric view, but also the Fcn choices in Plot views). This could become a bit of a can of worms… (And, from a certain viewpoint, the ”X” is a placeholder in F1(X) — it is, simply, the name of the variable to be used in the definition, and the Plot view works with functions from R to R [the name ”X” is bound within the definition and not visible from outside the definition].)

Perhaps some tick customization options could get you what you want: being able to add specific X values to a list (in Plot Setup) that would then be dashed lines in plot views. Comments?
Hello,
I've never tried "WHER" in Function Application. It is nice to know.
Thank you.
John P
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