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# David Wilson

### Auckland University of Technology

91 total contributions since 2011

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2D Convolution - Sobel Filter. What is wrong?
Here's my (old) code for a sobel filter: img = imread('Davis_Hall.jpg'); % 'Davis_Hall.jpg':color image X =double(rgb2gray(i...

4 giorni ago | 0

Related to Matlab Step Comment
You are possibly confusing the closed loop response with the open loop. The closed loop gain is 1/4, so the error is 1-1/4 = 3/4...

20 giorni ago | 1

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how to solve matrix differential equation
Here's my attempt: M = [ 97227/21875, 0, 82269/109375, 0, 67311/43750, 0, -97227/218750, 0; ... 0, 97227/21875, 0, 822...

27 giorni ago | 1

From Fir2 output to transfer function
tr_fun should be a discrete transfer function, (not continuous) say tr_fun=tf(BF,1,1); % Generate a DISCRETE Transfer Function...

circa un mese ago | 0

How to identify corners of data plotted to estimate data between corners
How about using interp1 with the 'pchip' option? You did speculate the interpolation is overly complex, but then again it is onl...

circa 2 mesi ago | 1

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How I can find co ordinates of intersection of two curves ?
Oh, looks like this is a common question: See (from 2016)https://au.mathworks.com/matlabcentral/answers/318475-how-to-find-the-i...

circa 2 mesi ago | 1

Iterative Method of solving multiple variables without using the curvefit tool
Here's my attempt at fitting uusing lsqcurvefit from the optimisation toolbox. First I generate some synthetic data to subsequ...

circa 2 mesi ago | 0

how can i calculate the angle of each gradient and x axis?
You could always differentiate to get the slope and then take the arc-tan. syms x real s = 1/(1 + exp(-2*(x-4))) dsdx = dif...

circa 2 mesi ago | 0

Extracting the daily time series from a text file to a single column
A quick hack is: fname = 'D59.txt' Flow = []; fid=fopen(fname); Yr = 2012; R = []; while 1 tline = fgetl(fi...

circa 2 mesi ago | 0

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How to Rearrange data?
Try something like the following: First read in the data file (which I've called numData.txt). I've used your test data above. ...

3 mesi ago | 0

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(Food for Thought) Peak Detection on ECG signal
OK, here's my (ugly) solution (withou using findpeaks). I've re-named your data set, and did some pre-processig. load ecg y =...

3 mesi ago | 0

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Simulating a FIR filter
Use the filter command. In this case your denominator, (A), coefficients are just 1. x = [ 0 0 0 1 1 1 1 1 ]' % input b = [...

3 mesi ago | 1

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Obtain input knowing output and transfer function
Since you have a simple transfer function, here's what I would do. (1) First generate some data that we will subsequently try ...

3 mesi ago | 0

curve fitting of non linear data for strain-time of creep experiment
Here's my attempt: load data1 t = time; e = strain; plot(t,e) %% Now try curve fit creep = @(p, t) p(1)*(1-exp(-p...

3 mesi ago | 0

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Trouble with time delay differential equation
I've only made one small change to your function. You have tried to index a non-integer number back, but the "Z" variable holds ...

3 mesi ago | 0

How can I simultaneously solve for these equations?
If you have the symbolic toolbox, a straight forward approach works, although it takes some time ... % ODE propblem syms B...

4 mesi ago | 0

Error when using ode15
It is good practice to try and avoid globals, but rather pass them as auxilary variables into the function. Fao = 1487.351; % ...

4 mesi ago | 0

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Plotting Step Response of a Differential Equation
You are close to a viable solution. Solve for an analytical solution, then make it a Matlab (anonymous) function with matlabFunc...

4 mesi ago | 0

Runge-Kutta 4th order method
First up, you will need a much smaller step size to get an accurate solution using this explicit RK4 (with no error control). I ...

4 mesi ago | 0

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How to draw Fig. 1 from the attached pdf with this code
I didn't bother draw the other 3 lines, but you just ned to make the necessary changes to gamma for that. If you run somethi...

5 mesi ago | 0

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fsurf not drawing cant explain
Do you really need to use the symbolic toolbox? Why not just plot a numerical surface? But you are right, your numbers are widel...

5 mesi ago | 0

Fitting Monod Equation with ODE45 to data using lsqcurvefit function
Here's my solution. First set up the measured data, plot it, and look to see that it is all OK. t = [0 3 5 8 9.5 11.5 14 16 ...

5 mesi ago | 0

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Solve integrals with Matlab
Do you have the symbolic toolbox? If so, start with the int command. You can do both indefinite and definite integration. sy...

5 mesi ago | 1

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MATLAB Help - Rolling Dice Simulation / Central Limit Theorem
A quick hack using randi and cumsum is N = 100 x = randi(6,N,6); cs = cumsum(x')'; for i=1:6 subplot(3,2,i) histogram...

5 mesi ago | 0

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How to calculate the accumulated rainfall value of 1, 2, 3, 4, 5, 6 and 7 days.
Here is my solution: I notice that you've got few NaNs for about a year and a half. Your last year is also incomplete. I is...

5 mesi ago | 0

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plot x axis as persentage
Below, I've plotted an arbitrary function between arbitrary limits, -5 and +37. %% x = linspace(-5,37)'; y = erf(x/20); ...

5 mesi ago | 0

inline function error help(tanh)
I can, but perhaps you should use anonymous functions. The inline approach is now discouraged. Instead of what you wrote above...

5 mesi ago | 0

how to plot multiple waves on one surface
Here is a mock up solution. Code is: below. I've used part of your data, but I've made up some similar data (using a sinc fun...

5 mesi ago | 0

LaTex with 2 strings separated by a num2str
Use an escape (backslash) for the % errordisplay=[' $\varepsilon_{RTP}=$ ',num2str(rtep),'\%'];

5 mesi ago | 1