What contourc function returns

[MengHuiHanTang]

This question is actually about Matlab, but the thing is I don't really use Matlab; Matlab is simply a labor for LabVIEW in the code. 

In Matlab, there is a function called c=contourc(im,[.8 .8]). This function is supposed to return a single contour at level 0.8. The return is a 2X387 matrix in this case. Can someone tell me what this matrix is? It does not look like a collection of pixle positions.  

Is there an efficient Matlab forum like this NI forum somewhere?

[James_M.]

Perhaps this Mathworks forum is what you're looking for:  http://www.mathworks.com/matlabcentral/answers/

James McNicol

Applications Engineer

National Instruments

[MengHuiHanTang]

James, 

Is there similar function in LabVIEW? I am trying to convert a m code into LV. Thanks.

[James_M. · Accepted solution]

Hi Meng Hui,

I'm not sure of the exact purpose of that Matlab function, but is this close to what you're looking to do?

https://www.ni.com/docs/en-US/bundle/ni-vision-labview-api-ref/page/imaqvision/imaq_extract_contour....

James McNicol

Applications Engineer

National Instruments

[MengHuiHanTang]

Thanks, James. 

That matlab function is used to return a contour, but I guess the difference is that the matlab contour function uses interpolation and therefore returns a DOUBLE contour line instead of Integer coordinates. 

[GregSands]

A function much closer to the Matlab one is included in LabVIEW 2011: Contour Line which is under the Mathematics/Geometry/Computational Geometry palette.  This works on 2D DBL arrays.

[MengHuiHanTang]

Greg, 

Thanks for the update. That's good to know. 

What is the input 'Height' for? Contour line is in a 2-D image. 

[GregSands]

Height specifies the value at which you want a contour.  Think of your 2D array as Z-values at a range of X-Y locations - then Height is the value of Z for contouring.  This is a polymorphic VI, so you can also provide an array of heights, or ask for a certain number of contours, and the heights will be automatically selected.  If you use those options, then the height of a given contour is returned in the Contour Line cluster as shown.