# Daniel Pollard

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**Content Feed**

why do I receive "Index in position 1 is invalid. Array indices must be positive integers or logical values"

i and j in MATLAB both have the default value of the complex unit. When you say for i = 1:26 you override this, so now i take...

9 mesi ago | 0

| accepted

Why vector created by colon have improper values

I'm struggling a bit to understand exactly what your question is but I think what you're asking is why the value 0.8 is not in y...

circa un anno ago | 1

why when i use find command to find the index i face problem

I had a play with my version of Matlab and found the same result. I think what you've stumbled on is a floating point error. The...

circa un anno ago | 0

All possible combination based on 2^n but with 1 and -1

You could take the answer from your previous question, subtract 0.5 and multiply by 2. Your accepted answer was n = 3; m = dec...

circa un anno ago | 0

How do I delete the last dimension of a 256*256*3 matrix?

Is Ii your 256x256x3 array? An image of 256x256 pixels will have 256x256x3 elements because of the red, green and blue elements....

circa un anno ago | 0

| accepted

Question

Is there a way to vectorise this vector/matrix product?

I have a piece of code inside a for loop, which looks like for k = 1:size(G, 1) G(k) = real(W(:,k)' * R * W(:,k)) end G ...

circa un anno ago | 2 answers | 0

### 2

answersCalculate power of exponential

Deleted my previous answer as I hadn't seen your edit so gave a wrong answer. You need a . before the multiplication symbol. Tr...

circa un anno ago | 1

| accepted

I want my solution as a Vector

Does this work? X(z) = R/N; instead of X = R/N

circa un anno ago | 0

| accepted

Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 1-by-1-by-2.

I haven't run it, but I think your code will error on the line deltaxj(i,ii,iii)=sum1+(x1-x1New)*(k.*(Rn+Rp)-dn)./dn; because...

circa un anno ago | 0

| accepted

How to error check a number for strings and blank inputs?

Are you looking for validateattributes or assert? For example, assert(menu == 1 || menu == 2) will throw an error if menu is n...

circa un anno ago | 0

FOR LOOP , beginner question.

Your code is d = []; for x=[0.1000,0.1500,0.2000] d=[d ((34.63/x)-5.126)/2.54]; disp ("ANSWER"); end x=[0.1000 0.1...

circa un anno ago | 0

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Can't calculate angle a, when 𝑠𝑖𝑛(𝑎)=2.

If a is a real number, then sin(a) must be between -1 and 1. Calling asin(2) returns 1.5708 - 1.3170i which is a complex num...

circa un anno ago | 2

| accepted

Array indices must be positive integers or logical values

You wrote psi(i,j) = ((U0*V0)./W)*cos(W(t-YY(i,j)./V0))-V0*XX(i,j); Try psi(i,j) = ((U0*V0)./W)*cos(W*(t-YY(i,j)./V0))-V0*XX(...

circa un anno ago | 0

| accepted

Solved

Find the largest number

Find the largest number |x| among 4 numbers given as variables |a|, |b|, |c|, and |d|. Example: Input: a = 4; b = 7; c ...

circa un anno ago

How to combine multiple curve fits in one plot?

https://www.mathworks.com/help/matlab/creating_plots/combine-multiple-plots.html This was literally the top result when I googl...

circa un anno ago | 0

Why is validateattributes returning me a Not enough inputs error only in this context?

I was assigning the class to a vector in reverse order, using a loop like for k = 16:-1:1 lsqsin(k) = LsqSinusoid(N_sample...

circa un anno ago | 0

| accepted

Question

Why is validateattributes returning me a Not enough inputs error only in this context?

I have a class definition called LsqSinusoid(n_samples, f, Fs). The constructor for that class takes three inputs - n_samples, t...

circa un anno ago | 1 answer | 0

### 1

answerWhile loop for testing the end of vector (Matlab)

If you know that it's 1-dimensional, you can use numel(vector) which returns the length of your vector. Also useful to know i...

oltre un anno ago | 1

Finding numChanges in array

Replace for i=1;length(V) with for ii = 1:length(V) The semicolon -> colon is a typo I suspect, and i has a built in value s...

oltre un anno ago | 1

| accepted

How to plot a graph in nm

Your method works perfectly well. An alternative option would be theta = 10 wavelength = [500:10:700] m = 1 d = (m.*waveleng...

oltre un anno ago | 1

| accepted

Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 10-by-10. not sure why i am getting this error

Biot_top is size 10x10. dtMat(1,j) is size 1x1. This means the LHS of your line is 1x1, and the RHS is 10x10, so you can't make ...

oltre un anno ago | 0

| accepted

How to create one errorbar for multiple data points?

If I understand you right, could you do something like figure; hold on plot(x, y, 'bx') errorbar(mean(x), mean(y), std(y), 'k...

oltre un anno ago | 1

| accepted

Graph with similar axis value with the value given

You want xticks and yticks. As a note: you need the vectors to be in ascending order, and your second tickmark vector isn't. so...

oltre un anno ago | 0

Does MathWorks have software for rocket trajectory modeling at supersonic speed?

The Aerospace toolbox is likely to be the closest to what you want. I don't use it so don't know much about it, but it seems to ...

oltre un anno ago | 0

converting degrees and radian

Something like option = input("Type A for degree to radians, and B for radians to degrees: ", 's') if option == "A" degs ...

oltre un anno ago | 0

How can I plot histogram?

Simply googling "matlab histogram" would have answered your question. That link is for the documentation for histogram. histog...

oltre un anno ago | 0

Double for loop is not working properly

k will take the values [1 2]. For the first iteration of k, it stores data{1,1}(:,14) in ch{1,n}. The second time around, it wil...

oltre un anno ago | 0

| accepted

Uneven linspacing of an array

If I understand right, you have a vector len, and you want to have a vector x such that diff(x)=len. In that case, you can use t...

oltre un anno ago | 0

Problem with running a Matlab code.

Clear your variables by putting the command clear at the start of your programme. It's almost certainly holding onto variable...

oltre un anno ago | 0

| accepted