How can I extract non-consecutive indices from a vector?

In 5.2 Extracting Multiple Elements, Further practice "Indices can be non-consecutive numbers. Try extracting the first, third, and sixth elements of density." How?

[Ahmad Ali]

p = density ([1,3,6])

[Panagiotis Papias]

Thank you @Ahmad Ali

[kavan dave]

thank you @Ahmad Ali

[Hardik Chauhan]

there is also a long way around

p=[density(1) density(3) density(6)]

[Jingliang Zhang]

p = transpose([density(1) density(3) density(6)])

[Namratha priya S R]

just

p=density([1 3 6])

[RAJNISH KUMAR]

Nice 👌👌

[Arjun Sabu]

Great

[Kevin Kipkorir]

thank you

[Min]

It's helpful!

[Tadele]

Thank you

[Ishaan]

thanks@Ahmad Ali

[Edward li]

Could someone explain the logic behind the parenthese and the brackets. like why is it in that order and what does each mean?

[Voss]

@Edward li: In this case, the parentheses are used for indexing, and the square brackets are used for array concatenation. [1,3,6] concatenates the scalars 1, 3, and 6 into a single vector, and density([1,3,6]) gets the elements of density at the indices stored in that vector.

See the Special Characters section of this page for more information:

https://www.mathworks.com/help/matlab/matlab_prog/matlab-operators-and-special-characters.html

Answer 1

[David Hill]

If you have a density array (d), then to extract the 1,3,6 elements:

extracted_elements=d([1,3,6]);

[Stefan Rusu]

Tnx!

[Rodolfo Torres]

extracted_elements=density([1,3,6])

It didn´t work

[Pranab Dey]

It did not work.

[Namrata Verma]

worked

[Santos Joao]

If it doesn't try updating all the tasks first then try again.

[Puniit Chaudhri]

Thanks

[Karen Raymond]

This worked for me..

p = [density(1);density(3);density(6)]

[Nasser Abdelghani]

Thank you

[Dan]

MathWorks needs to work on this on-ramp. This was clear as mud, as they say...

[Larry Spencer]

Yes, I was confused too. I'm 99% sure this notation was not covered in the preceding material.

[Rohit Punetha]

there should not be - ;

[Ahmed Husnain]

Cool, it worked

[Dinesh Kudva]

this works, but how?

[Furkan Akbal]

k=[1 3 6]
extracted_elements=density(k)

it worked because we couldn't specify from the syntax which elements the code should extract. we solved this problem by assigning positions to vector or making them an element

[tamana]

thankyou

[Vincenzo]

density([1 3 6])

[Mostafa]

parentheses and inside brackets was the solution all along... I have spent 30 minutes trying to figure out without looking it up. cheers David

[Vinayak kumar]

it can be done without commas

[Viktoriia]

no it can't. It only worked for me when I used commas.

[Image Analyst]

@Viktoriia observe it working without commas below:

d = 10 : 10 : 60 % Sample data vector.

d = 1×6

10 20 30 40 50 60

extracted_elements = d([1 3 6]) % Get only some of the elements

extracted_elements = 1×3

10 30 60

If you execute that code on your computer what do you see? If you executed different code than above, without commas, then what was that code?

Answer 2

[Kakasaheb Nikam]

density(3)

% extract third element

when we use [ ] square bracket, it extracting specific index position values.

so answer is

extracted_elements = density( [ 1, 3, 6 ] );

[MAHMUDUL FIROZ]

density( [ 1, 3, 6 ] )

[Ume Aiman]

yess this is correct

Answer 3

[shaik sahil]

p=density([1,3,5])

[Md Asif Rezwan Shishir]

p=density([1,3,6])

it worked for me...thanks!

Answer 4

[Diogo Teixeira Fernandes]

extracted_elements=density([1,3,6])
it worked for me

Answer 5

[Girish Pal]

p = density(1), density(3), density(6)

[madhan ravi]

What?

[Stephen23]

While this does literally what the question requests "...extract non-consecutive indices from a vector", it only assigns the first of the comma-separated list to p, which is unlikely to give the desired effect, nor is it likely to be what the homework task requires.

Answer 6

[Jamal Ahmad]

p=density( [ 1, 3, 6 ] )

[madhan ravi]

How's this different from other answers?

Answer 7

[Harish Mirji]

density = [5 8 9 7 8 4 5 9 8 7]

density = 1×10

5 8 9 7 8 4 5 9 8 7

p = density([1 3 5])

p = 1×3

5 9 8

[Abubakarr]

It worked for me, thanks.

Answer 8

[Ahmed]

Extracting Multiple Elements

Instructions are in the task pane to the left. Complete and submit each task one at a time.

This code sets up the activity.

data = [3 0.53 4.0753 NaN;18 1.78 6.6678 2.1328;19 0.86 1.5177 3.6852;20 1.6 3.6375 8.5389;21 3 4.7243 10.157;23 6.11 9.0698 2.8739;38 2.54 5.30023 4.4508]

data = 7×4

3.0000 0.5300 4.0753 NaN 18.0000 1.7800 6.6678 2.1328 19.0000 0.8600 1.5177 3.6852 20.0000 1.6000 3.6375 8.5389 21.0000 3.0000 4.7243 10.1570 23.0000 6.1100 9.0698 2.8739 38.0000 2.5400 5.3002 4.4508

density = data(:,2)

density = 7×1

0.5300 1.7800 0.8600 1.6000 3.0000 6.1100 2.5400

x = density([1,3,6]) 

x = 3×1

0.5300 0.8600 6.1100

Answer 9

[Parvin]

This code sets up the activity.

data = [3 0.53 4.0753 NaN;18 1.78 6.6678 2.1328;19 0.86 1.5177 3.6852;20 1.6 3.6375 8.5389;21 3 4.7243 10.157;23 6.11 9.0698 2.8739;38 2.54 5.30023 4.4508]

data = 7×4

3.0000 0.5300 4.0753 NaN 18.0000 1.7800 6.6678 2.1328 19.0000 0.8600 1.5177 3.6852 20.0000 1.6000 3.6375 8.5389 21.0000 3.0000 4.7243 10.1570 23.0000 6.1100 9.0698 2.8739 38.0000 2.5400 5.3002 4.4508

To extract the first, third, and sixth elements of density, use [1 3 6] as an index.

density = [1 3 6]

density = 1×3

1 3 6

data(density)

ans = 1×3

3 19 23