# Wolfgang Schwanghart

### University of Postdam

Professional Interests: GIS, Physical Geography, Hydrology, Geomorphology

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**Content Feed**

Question

Fit Gaussian mixture model with weighted observations

Hi everyone, looking at the help of fitgmdist, I cannot see that there is the possibility to weight observations. Is there a rea...

circa 2 anni ago | 3 answers | 0

### 3

answers2D gaussian filter with a variable sigma

Hi Chad, below is some code that does the trick using nlfilter. To be more efficient, I created a look-up table with a finite s...

circa 3 anni ago | 0

What makes a Toolbox a Toolbox, and how is it recognized by Matlab?

Hi Chad, the trick is to have a Contents.m-file in the main folder of your toolbox. In TopoToolbox, the file starts with T...

oltre 3 anni ago | 0

Question

Customized icons in workspace

Hi all, I have written a couple of MATLAB classes and, as icing on the cake, I'd like to have customized icons in the worksp...

circa 8 anni ago | 0 answers | 1

### 0

answerstotal number of elements which are not zero

Hi, what about: B = sum(Percey~=0,2); Regards, W.

oltre 9 anni ago | 0

| accepted

How can I perform a comparison function (of surrounding pixels) on a DEM using a starting pixel?

Hi, you might be interested in using the function ixneighbors available on the FEX which might make life a little easier for ...

oltre 9 anni ago | 0

Connected graph given adjacency matrix

You can use the function dmperm to see if a graph consists of one or several connected components. E.g. see the example here <h...

oltre 9 anni ago | 0

| accepted

path elevation profile

Hi, if you have the image processing toolbox, the function improfile should do what you ask for. <http://www.mathworks.de/help/...

circa 10 anni ago | 0

plotting more data from large data

Hi doc gscatter hope this helps. Regards, W.

circa 10 anni ago | 0

What does +(A>0) do?

I often do this to convert a logical matrix to double. However, I just tried and realized that this is slower than A = double(A>...

oltre 10 anni ago | 1

error using imsubtract

Hi Megah, apparently both variables don't have the same class. Try image3 = imsubtract(im2double(image1),im2double(BWfinal)...

oltre 10 anni ago | 0

Calculate the indirect distance between two points

Bahare, you might find this contribution interesting: <http://www.mathworks.com/matlabcentral/fileexchange/8625-shortest-pat...

oltre 10 anni ago | 0

Ordered connected components

Hi Dustin, I don't have MATLAB at hand right now, so I cannot try, but I think bwboundaries should solve your problem. [...

oltre 10 anni ago | 0

Graph analysis question

I just tried your example. While results of a kmeans clustering don't look too promising, the function clusterdata works quite w...

oltre 10 anni ago | 0

Overlay digital elevation model on hillshade

Hi Ajay, you might want to check TopoToolbox, which includes such a function. <http://physiogeo.unibas.ch/topotoolbox/> ...

oltre 10 anni ago | 0

Count black and white pixels on a image

How about using *blockproc* to get the number of white pixels (in case you have the image processing toolbox)? A = full(spran...

oltre 10 anni ago | 0

Question

Keeping k largest values in each column of a sparse matrix

Hi everyone, I am trying to implement an algorithm that involves a pruning of a large sparse matrix. The pruning scheme shoul...

oltre 10 anni ago | 1 answer | 0

### 1

answerdata correction

Hi, you can identify the NaNs using the function isnan. I = isnan(dem); % where dem is the digital elevation model The inpa...

oltre 10 anni ago | 0

Problem on fuzzy inference calculations ..

Hi, the error message says all: The first input must be a defined DOUBLE matrix Is the variable input in double format? ...

oltre 10 anni ago | 1

| accepted

finding neighbor of a position

Hi, you might find this function useful. <http://www.mathworks.com/matlabcentral/fileexchange/16991-neighbor-indexing> ...

oltre 10 anni ago | 1

Connect bwlabeled components

I'd start with using the function bwlabeln to label the connected components in the 3d. This, however, requires them to never ov...

oltre 10 anni ago | 0

straighten curved Image

This is not trivial and I think you should show what you have done so far. If you haven't really started yet, you may want to lo...

oltre 10 anni ago | 0

how to draw a grid in MATLAB???

Hi, take a look at Steve's blog, where he describes how to generate a pixel grid. Perhaps, this is what you want. <http://...

oltre 10 anni ago | 1

Kriging

To my knowlegde there is no comprehensive geostatistical software written in Matlab. I would always use packages such gstat or g...

oltre 10 anni ago | 2

How to plot a 2D vector-field and exclude zero-vectors (dots) in the graph?

How about: I = ~(T(:,3)==0 & T(:,4)==0); quiver(T(I,1),T(I,2),T(I,3),T(I,4)); cheers, Wolfgang

oltre 10 anni ago | 2

| accepted

Is there a way to prevent or circumvent the formation of long edges in a Deluanay Triangulation?

Hi AJP, without knowing what exactly yoou want to do, I like to link to a tool that was extremely helful to me. <http://w...

oltre 10 anni ago | 0

TSP using GA

If this is so urgent for you, did you anything to find available code? Apparently not. Searching google with "tsp matlab ga" dir...

oltre 10 anni ago | 0

Edge direction

Hi, to extract edges of any direction, you just need to choose the right structuring element for a morphological opening. E....

oltre 10 anni ago | 3

| accepted