onrammp exercise 14.2 stellar motion part 2, task 6 movaway

Question

Darnell Gawdin 2020-1-3

3
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/498765-onrammp-exercise-14-2-stellar-motion-part-2-task-6-movaway

回答： tania 2024-3-12

采纳的回答： KALYAN ACHARJYA

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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)

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Nikita 2024-2-12

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.

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Answer 1

KALYAN ACHARJYA 2020-1-3

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https://ww2.mathworks.cn/matlabcentral/answers/498765-onrammp-exercise-14-2-stellar-motion-part-2-task-6-movaway#answer_408575

编辑：KALYAN ACHARJYA 2020-1-3

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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)

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Darnell Gawdin 2020-1-3

Thank you for your time and expertise to answer this question. I see how it works now.

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Answer 2

Bongani Tavengwa 2020-6-5

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https://ww2.mathworks.cn/matlabcentral/answers/498765-onrammp-exercise-14-2-stellar-motion-part-2-task-6-movaway#answer_446846

编辑：DGM 2023-2-22

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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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Meifeng 2022-7-30

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for v=1:7
    s=spectra(:,v)
    if speed(v)<= 0
        plot(lambda,s,"--")
    end
    hold on
end

Narmadha 2023-9-9

Add an else statement. If speed(v) is greater than 0, create a plot of s against lambda using a line width of 3.

After the for loop, enter hold off.

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Answer 3

tania 2024-3-12

0
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https://ww2.mathworks.cn/matlabcentral/answers/498765-onrammp-exercise-14-2-stellar-motion-part-2-task-6-movaway#answer_1424291

在 MATLAB Online 中打开

Habiendo creado un script en tiempo real para encontrar el desplazamiento al rojo, puede modificar fácilmente este script para repetir el cálculo con cualquier estrella de la matriz spectra.

ACTIVIDAD

Modifique la sección Tasks 2 & 7 del script para que realice el cálculo del desplazamiento al rojo con la segunda estrella de spectra en lugar de la sexta.

s = spectra(:,2)
[sHa,idx] = min(s)
lambdaHa = lambda(idx)
z = lambdaHa/656,28 - 1
velocidad = z*299792.458
Test Results:
¡Incorrecto!
¿Es s la segunda columna de spectra?
¿Tiene lambdaHa el valor correcto?
¿Tiene speed el valor correcto?
cual es el error ???