gnuplot-info

[Gnuplot-info] Gnuplot doesn't show me the right x-axis intersection of a function

[Luigi <dri...@li...>]

Hi. I was trying to plot the following function:

-0.9+9.638x^(-1.394)

by using the command

plot y=-0.9+9.638x**(-1.394)

The problem is that the intersection with the x-axis (y=0) should be at 
around x=5.47, but the function's plot just approaches y=0 as an asymptote.

When I try to plot it with Maxima, the intersection is correct.

Is there something wrong in the syntax of the command? Thanks.

Re: [Gnuplot-info] Gnuplot doesn't show me the right x-axis intersection of a function

[Dr. I. D. J. <die...@t-...>]

Hi Luigi,
I am sure you did something wrong. First of all, your formula is erratic as it 
should be

f(x)=-0.9+9.638*x**(-1.394)

please note the "*" between the factor (9.638) and the power of x ...

secondly the command plot y= something does not work, what you ought to do is 
either 

plot -0.9+9.638*x**(-1.394) w l lw 2

or say

f(x)=-0.9+9.638*x**(-1.394)
plot f(x) w l lw 2

to provide an example. In both cases I get the zero crossing around x=5.479

Hope this helps,
take care




Dieter Jurzitza

On Samstag, 18. August 2012 23:06:27 Luigi wrote:
> Hi. I was trying to plot the following function:
> 
> -0.9+9.638x^(-1.394)
> 
> by using the command
> 
> plot y=-0.9+9.638x**(-1.394)
> 
> The problem is that the intersection with the x-axis (y=0) should be at
**************
-- 
-----------------------------------------------------------

                               |
                                \
                 /\_/\           |
                | ~x~ |/-----\   /
                 \   /-       \_/
  ^^__   _        /  _  ____   /
 <°°__ \- \_/     |  |/    |  |
  ||  ||         _| _|    _| _|

if you really want to see the pictures above - use some font
with constant spacing like courier! :-)
-----------------------------------------------------------

Re: [Gnuplot-info] Gnuplot doesn't show me the right x-axis intersection of a function

[Jefferson S. E. P. <st...@gm...>]

Hi Luigi,

to what Dieter Jurzitza already said I only add that you'll see better
your intersection with the x-axis if you adjust the range of the plot,
for example:
  set xrange [0:10]
  set xrange [0:10]
  plot -0.9+9.638*x**(-1.394) w l lw 2
With the default ranges all you'll see is indeed that divergence of
your function as x->0.

Cheers,
Jefferson


On Sat, Aug 18, 2012 at 11:06 PM, Luigi <dri...@li...> wrote:
> Hi. I was trying to plot the following function:
>
> -0.9+9.638x^(-1.394)
>
> by using the command
>
> plot y=-0.9+9.638x**(-1.394)
>
> The problem is that the intersection with the x-axis (y=0) should be at
> around x=5.47, but the function's plot just approaches y=0 as an asymptote.
>
> When I try to plot it with Maxima, the intersection is correct.
>
> Is there something wrong in the syntax of the command? Thanks.
>
> ------------------------------------------------------------------------------
> Live Security Virtual Conference
> Exclusive live event will cover all the ways today's security and
> threat landscape has changed and how IT managers can respond. Discussions
> will include endpoint security, mobile security and the latest in malware
> threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/
> _______________________________________________
> gnuplot-info mailing list
> gnu...@li...
> https://lists.sourceforge.net/lists/listinfo/gnuplot-info