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Re: Questions about NG image with (log) axis [message #85444 is a reply to message #85441]

Wed, 07 August 2013 02:22

Xin Tao
Messages: 40
Registered: April 2011

Member

Thank you very much, Fab.

The purpose of dlinear is to create an array (in my case) from 10 to 100 linearly with 300 elements.
It's equivalent to

x=10.0+dindgen(300)*(100-10.0)/(300-1)

Best,

Xin

On Wednesday, August 7, 2013 2:53:30 PM UTC+8, Fabien wrote:
> Hi Xin Tao,
>
>
>
> On 08/07/2013 08:38 AM, Xin Tao wrote:
>
>> data = dist(300)
>
>>
>
>> My question 1: What determines the size of the image?
>
>> If I have
>
>>
>
>> x=dindgen(300)*2
>
>> y=dindgen(300)
>
>>
>
>> then im=image(data, x, y, axis_style=2) will give me an elongated image.
>
>>
>
>> If I have
>
>> x=dindgen(300)
>
>> y=dindgen(300)
>
>>
>
>> then im=image(data, x, y, axis_style=2) will give me an square image.
>
>>
>
>> This behavior of the IMAGE function is strange to me.
>
>
>
> This is documented here I think:
>
>
>
> ASPECT_RATIO
>
> A floating point value indicating the ratio of the Y dimension to the X
>
> dimension in data units. If this property is set to a nonzero value, the
>
> aspect ratio will be preserved as the graphic is stretched or shrunk.
>
> The default value is 0 for all graphics except images, meaning that the
>
> aspect ratio is not fixed, but is allowed to change as the graphic is
>
> stretched or shrunk.
>
>
>
> IDL> y=dindgen(300)
>
> IDL> x=dindgen(300)*2
>
> IDL> im=image(data, x, y, axis_style=2, ASPECT_RATIO=2.)
>
>
>
> is quadratic
>
>
>
>>
>
>> My question 2: This looks like a bug.
>
>>
>
>> If I have
>
>>
>
>> x=dlinear(10, 100, 300) ;; create an array from 10 to 100 with 300 elements
>
>> y=dindgen(300)
>
>>
>
>> and
>
>>
>
>> im=image(data, x, y, /xlog, axis_style=2)
>
>>
>
>> the image x axis has a value from 10^20, 10^40, ..., 10^100. This is certainly wrong to me.
>
>
>
> I don't know what dlinear does so I can't say anything here.
>
>
>
> Cheers,
>
>
>
> Fab

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[Message index]

		Questions about NG image with (log) axis By: Xin Tao on Tue, 06 August 2013 23:38
		Re: Questions about NG image with (log) axis By: Fabzi on Tue, 06 August 2013 23:53
		Re: Questions about NG image with (log) axis By: Xin Tao on Wed, 07 August 2013 02:22
		Re: Questions about NG image with (log) axis By: Fabzi on Wed, 07 August 2013 04:59
		Re: Questions about NG image with (log) axis By: Xin Tao on Wed, 07 August 2013 05:10
		Re: Questions about NG image with (log) axis By: chris_torrence@NOSPAM on Thu, 15 August 2013 10:37
		Re: Questions about NG image with (log) axis By: David Fanning on Thu, 15 August 2013 10:52
		Re: Questions about NG image with (log) axis By: Xin Tao on Thu, 15 August 2013 20:28

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