topic Re: What contourc function returns in LabVIEW

What contourc function returns

MengHuiHanTang — Wed, 10 Aug 2011 13:48:49 GMT

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?

Re: What contourc function returns

James_M. — Thu, 11 Aug 2011 15:32:38 GMT

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

James McNicol

Applications Engineer

National Instruments

Re: What contourc function returns

MengHuiHanTang — Fri, 12 Aug 2011 16:50:40 GMT

James,

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

Re: What contourc function returns

James_M. — Tue, 30 Jun 2026 18:00:18 GMT

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.html

James McNicol

Applications Engineer

National Instruments

Re: What contourc function returns

MengHuiHanTang — Tue, 16 Aug 2011 13:21:01 GMT

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.

Re: What contourc function returns

GregSands — Tue, 30 Jun 2026 18:00:36 GMT

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.

Re: What contourc function returns

MengHuiHanTang — Wed, 17 Aug 2011 13:24:08 GMT

Greg,

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

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

Re: What contourc function returns

GregSands — Wed, 17 Aug 2011 23:28:40 GMT

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.