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onrammp exercise 14.2 stellar motion part 2, task 6 movaway
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For task 6 I don't understand how matlab connects starname to a particular graph.
Also I'm not sure how this piece of code works...
"movaway = starnames(speed < 0) "
how does this line of code use a variable that is in a loop before this line of code?
Sorry in advance if this is an obvious question.
Task 1
[sHa,idx] = min(spectra);
lambdaHa = lambda(idx);
z = lambdaHa/656.28 - 1;
speed = z*299792.458
Tasks 2 - 4
for c = 1:7
s = spectra(:,c);
if speed(c) >= 0
loglog(lambda,s,"--")
else
loglog(lambda,s,"LineWidth",3)
end
hold on
end
hold off
Task 5
legend(starnames)
Task 6
movaway = starnames(speed < 0)
1 Comment
Nikita
on 12 Feb 2024
Add an if statement to the for loop body. If speed(v) is less than or equal to 0, create a plot of s against lambda using a dashed line (--).
Add the command hold on between the two end keywords so that you only create one plot.
Accepted Answer
KALYAN ACHARJYA
on 3 Jan 2020
Edited: KALYAN ACHARJYA
on 3 Jan 2020
See the example, lets suppose starnames is variable having all types of numbers
starnames=[-2 3 45 7 2 0 -4 5 7 7 6 9];
speed=[2 3 -4 5 6 7 8 0 5 2 -30] ; % Just random example
## speed<0 is an conditional assignment, its return a logical array (with 0 & 1), when condition true, its 1, otherwise 0
>> speed < 0
ans =
1×11 logical array
0 0 1 0 0 0 0 0 0 0 1
## starnames(speed < 0) return an array, where the 1 presence in the above logical array
>> movaway = starnames(speed < 0)
movaway =
45 6
This is just an example to understand the issue (This approach is good way for efficient code, conditional & array indexing)
1 Comment
More Answers (1)
Bongani Tavengwa
on 5 Jun 2020
Edited: DGM
on 22 Feb 2023
Task
Add an if statement to the for loop body. If speed(c) is less than or equal to 0, create a loglog plot of s against lambda using a dashed line (--).
After the if statement, add the command hold on so that only one plot is created.
for c = 1:7
s = spectra(:,c);
if speed(c) >= 0
loglog(lambda,s,"--")
else
loglog(lambda,s,"LineWidth",3)
end
hold on
end
please help me where do i go wrong
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