# Jakob Sørensen

### Technical University of Denmark

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Professional Interests: 3D imaging, Image analysis

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Paraboloid minimum point always becomes (0,0)

x1 = 1 | y1 = 2.25 x2 = 2 | y2 = 3.25 x3 = 3 | y3 = 3.25 x4 = 4 | y4 = 4.25 x = [x1 x2 x3 x4]; y = [y1 y2 y3 y4...

10 years ago | 0

Question

Paraboloid minimum point always becomes (0,0)

Hi, I'm trying to do linear regression, by minimization of the squared errors. I.e. by minimizing the following pseudo-code ...

10 years ago | 2 answers | 0

### 2

answersI got error in the script..

Can you tell us what data type the image is, after loading it (the *img* variable). You can usually see it in the upper right co...

10 years ago | 0

UIContextMenu disabled when axes is used

It solved it to add the *uicontextmenu* to the image, rather than to the axes. So when displaying the image, add the menu: ...

10 years ago | 0

| accepted

Question

UIContextMenu disabled when axes is used

Hi there, I've created a small GUI using the GUIDE tool (its the lazy way, I know). I have an axes I use to show an image, an...

10 years ago | 1 answer | 0

### 1

answerRegression with some part of the array

x = [ 1 5 6 7 8 3 2 ]; y = [ 2 9 4 6 4 5 6 ]; idx = find(x > 3); % Returns the indexes where x is larger than 3 ...

10 years ago | 0

| accepted

Question

Colormap is not applied correctly

Hi there, I'm having a really odd issue when loading and showing my own GIF and PNG images. It seems that when the colormap i...

10 years ago | 0 answers | 1

### 0

answersQuestion

LibSVM - Which hinge loss function?

Hi there, I was wondering if anyone knows what <http://en.wikipedia.org/wiki/Hinge_loss hinge loss> function <http://www.csie...

10 years ago | 0 answers | 0

### 0

answersGUI full screen with centred figure?

It is definitely possible to get the figure size using *get(gcf, 'position')*, and then calculate where the figure position shou...

10 years ago | 0

Question

Order of indexes when using rgb2ind

Hi there, I have some classified images in tif format (usually 3-4 classes), which I need to import to Matlab as an indexed i...

10 years ago | 1 answer | 0

### 1

answeris there a code to open and run all m files in a folder?

I don't know if there is a built-in function, but I think you could fairly easy make one yourself. Using the command *<http://ww...

10 years ago | 1

Question

Selected multiple values from a matrix

Lets say i got a 10x10 matrix, lets call it *M* , and I want to select the data from [a,b] and [c,d]. Of course i could do this ...

10 years ago | 1 answer | 1

### 1

answerHow to use svmpredict (libsvm)

For further reference I figured it out myself. The *testing_label_vector* can be added to calculate the accuracy of the predicti...

10 years ago | 5

| accepted

Question

Coloring a surf() plot by value

Hey all, I've made a surf plot of training times for an SVM, depending on values of C and gamma (so C and gamma as x and y, a...

10 years ago | 0 answers | 0

### 0

answersQuestion

Changing the color of specific points in a scatter plot

Hey, I got some points in a 2-dimensional space from two different classes. I got a label vector to identify which points bel...

10 years ago | 1 answer | 0

### 1

answerHow to plot 16x16 pixel image from RGB data available in Excel Sheet?

If I understand correctly, each sheet has the red (R) value in the first column, the green (G) value in the second and the blue ...

10 years ago | 1

| accepted

How to plot 16x16 pixel image from RGB data available in Excel Sheet?

Have a look at this artcile, regarding <http://www.mathworks.se/help/matlab/import_export/import-a-worksheet-or-range-with-xlsre...

10 years ago | 0

Question

How to use svmpredict (libsvm)

Hey, I'm trying to use libsvm in Matlab, but I am a bit confused regarding the *svmpredict()* function. The first input to it...

10 years ago | 1 answer | 3

### 1

answerQuestion

svmclassify is extremely slow

Hey there, I'm trying to use the built-in Support Vector Machine (SVM) tools in Matlab to classify an image. Its a 1000x1000(...

11 years ago | 1 answer | 0

### 1

answerQuestion

Margins around histogram in subplot

I'm trying to make a 2x3 subplot, where the top 3 fields are merged to contain an image, and the bottom 3 fields are used for hi...

11 years ago | 1 answer | 0

### 1

answerQuestion

Scaling a function (wavelet)

Hi there, I got a function descriped as follows: t = linspace(-3, 3 1024); % Time vector from -3s to 3s with 10...

11 years ago | 0 answers | 0

### 0

answersplot two data sets over different time in the same plot

Here is an example of how it can be done: t1 = linspace(0,2*pi,100); t2 = linspace(pi,2*pi,50); y1 = sin(t1); ...

11 years ago | 0

Question

Adding custom wavelets to cwt

Hi there, *Summary:* _How do I take a custom signal *y* and turn it into a wavelet for *cwt*?_ *Long version:* I'm looki...

11 years ago | 5 answers | 1

### 5

answersQuestion

Shepp-Logan filtering (spatial domain)

Hey there, I got a school assignment where I have to re-construct a CT image, using filtered backprojection. It is specif...

12 years ago | 1 answer | 0

### 1

answercalling a function for a number of indexes in a matrix

Can't you just get a logical of where the matrix is above/below the thresh? And then multiply it with your matrix. And then do t...

12 years ago | 0

Question

Combining two images (ultrasound blood flow)

Hey there, I'm doing a project on blood flow velocity in ultrasound. I Need to display a color flow map, with a colorbar dis...

12 years ago | 0 answers | 0

### 0

answersQuestion

Filter coefficients from poles

Hey, I'm looking to make an AR (all-pole) filter. I would like to be able to select poles by coordinates, and get the filter...

12 years ago | 1 answer | 0

### 1

answerIIR filter from diff. equation

Oka, I have been looking at it, over and over again, and I think I need some more help... The algorithm I'm trying to imple...

12 years ago | 0

Question

IIR filter from diff. equation

Hey, I got a rather silly problem. I got the difference equation of a transfer function, and I need to create a filter from ...

12 years ago | 3 answers | 0

### 3

answersQuestion

Variable called angle (name conflict)

I got a .mat file containing some data, some of which are single value variables. One of these are called 'angle' which conflict...

12 years ago | 1 answer | 0