# Transforming axis. How to create a customized axis.

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Chandel Singh 2019 年 1 月 22 日
コメント済み: Jan 2019 年 2 月 11 日
I have x,y,z coordinates from a tissue and corresponding them, a signal value. The tissue is curved, so when I plot data in x-y plane, I can see the graph as shown. I want to plot 2D graph such that my x-axis is the midline of tissue(black line) and y-axis is my signal value.
Thanks!

#### 8 件のコメント

Jan 2019 年 1 月 31 日
"Axis" means a straight line. Therefore we still have to guess, which line you mean.
To 1) It depends on how you draw in the image. But after drawing, the coordinates should be available directly.
To 2) It depends. If you mean a manually drawn line, this will not be straight necessarily. Then there is no unique transformation to a line. You could e.g. draw a circle, or a curve, which is intersecting itself. This should show immediately, that a unique definition of such a transformation is not possible. So please explain, what you want to achieve.
Chandel Singh 2019 年 2 月 10 日
i apologize for the way i had described problem earlier. Hopefully the current way might make it clear
defining problem once more :
the data has x,y coordinate and a cooresponding value signal value to it(shown in figure in black is the contours of the data in xy plane). The objective is to plot the data along a handrawn curve.
These are the goals:
1) to draw a curve on image by hand
2) extract it’s corrdinates
3) then fit a curve of the form y =f(x), where f(x) can be a polynomial or any function which approximates the handrawn curve using the extracted coordinates.
• 2nd point is not required if we can directly fit a curve.
4) plot the data along this new curve( as illustrated in figure )
map all the points such that y coordinte is the perpendicular distance of the pojnt from the curve and x coordinate is the aling thr curve from an end of the curve.
Jan 2019 年 2 月 11 日
@Chandel Singh: So start with finding a function to fit the hand drawn curve. This is not trivial and there is no unique solution. What about a cubic spline or are there any mathematical restrictions to the wanted function?
Afterwards a problem remains: in the parts, where the function is konvex, the relation is not necessarily unqiue. Example: If the fitted line is a circle, you cannot find a unique correlation between the curve and the center. This means, that there is no guarantee that there is a unique solution to you problem.
But you can find some solutions. Currently this problem does not concern Matlab, so you have to find mathematical solutions any where elese at first, before it matchs the topic of this forum.

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### 回答 (2 件)

jahanzaib ahmad 2019 年 1 月 22 日
you want to move x-axis to middle of graph ?

#### 1 件のコメント

Chandel Singh 2019 年 1 月 31 日
No

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jahanzaib ahmad 2019 年 1 月 22 日
minus some value from x coordinates
like if u have x,y data in A .
A =[A(:,1)-1321 A(:,2)];

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