For loop cycle struct

i have a struct which consist of 10 sets of data, i.e struct(1), struct(2).......

I need to extract certain bits of data from each data set to use in a formula.

as an example:

struct(1).Mass = 200 struct(1).Distance=50

struct(2).Mass = 350 struct(2).Distance=100

struct(3).Mass = 400 struct(3).Distance=150

now if i had an equation such as: if struct(1) %<<<<<<The user selects their struct

Mass1=200

Mass2=(i) %<< this cycles and presents all the possibilities for Mass. i.e 350, 400

similar with distance. If struct(1)

Distance1=50

Distance2=(j) %<<<<<<This cycles and presents all possibilities for Distance. i.e 100, 150

If the equation was: (Mass1 * Mass2) / (Distance 1 - Distance 2).

How can i make it loop so that it presents all of the output as a list. such as:

input(struct(1))

(200 * 350) / (50 - 100) = -1400

(200 * 400) / (50 - 150) = -800

As i stated i would have 10 of these lines. the example scenario is to help me grasp the concept of whats needed to implement a loop system that presents the list of solved equation as shown above.

I would appreciate any help regarding this.

Answer 1

[Stephen23]

This is MATLAB, so it is simpler to avoid using a loop:

>> S(1).Mass = 200; S(1).Dist=50;
>> S(2).Mass = 350; S(2).Dist=100;
>> S(3).Mass = 400; S(3).Dist=150;
>> idx = 1; % user selected index.
>> idv = setdiff(1:numel(S),idx);
>> num = (S(idx).Mass * [S(idv).Mass]);
>> den = (S(idx).Dist - [S(idv).Dist]);
>> out = num ./ den
out =
  -1400   -800

Read about how this works:

https://www.mathworks.com/help/matlab/matlab_prog/vectorization.html

https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

[Alias:Max]

I am still struggling. Perhaps a better explanation of what i want to achieve.

i have a struct labelled solar.

In solar it has 10 data sets each set has 4 variables:

 #   Name, (Mass(m), Diameter, Distance (d) ) each name has these 3 variables of numeric data.
1 Sun
2 Mercury
3 Venus
4 Earth
5 Mars
6 Jupiter
7 Saturn 
8 Uranus
9 Neptune
10 Pluto

The user inputs the name they want i.e (sun)

now this uses a formula

F=G*(m1*m2)/((d1 - d2)^2) %<<< formula for gravitational                 %force(measured in Newtons)

But it requires all mass(m) and distance(d) for each name excluding the input name.

I need it to cycle / loop so the end result would be listed as:

input (Sun)
The gravitational force between the Sun and other celestial bodies are:
Mercury     123N %<< these are example values
Venus        234N
Earth         345N
Mars           456N
Jupiter        567N
Saturn        678N
Uranus        789N
Neptune       891N
Pluto            912N

This list is then going to use a sort function to display the list in descending order.

My effort is:

CB1 %<<< user input variable
if CB1(1,1)=='S' <<<< Sun
    m1=solar(1).Mass
    m2=solar(i).Mass
    d1=solar(1).Distance
    d2=solar(j).Distance
elseif CB1(1,2)=='e' %<< 2nd letter in mercury, as M would conflict with %Mars
    m1=solar(2).Mass
    m2=solar(v).Mass
    d1=solar(2).Distance
    d2=solar(d).Distance
end

This is writen for each input variable.

these values should then cycle through a function, using the formula above and display the output. As a list.

Sorry for long response but ithought it would provide better clarity.

Thanks in advance

[Steven Lord]

I would instead store the data in a table array with appropriate RowNames. See for example the "Specify Row Names" example on the table documentation page for an illustration of how to set and use row names.

[Stephen23]

See also new question here:

https://www.mathworks.com/matlabcentral/answers/441746-loop-structure-variables-in-formula