need help with this task in matlab onramp final project

[sHa,idx] = min(spectra);
lambdaHa=lambda(idx);
z=lambdaHa 1656.28-1;
speed=2*299792.958

for v=1:7
    s = spectra(:'v)
end

This is the part that I keep getting stuck on:

Add it statement to the for loop body if speed (v) is less than or equal to 0

Create a plot of s against lambda using dashed line (--)

Add hold on command between two end keywords.

* So this is what I put down*

if speed(v) <= 0
    plot(lambda, s, "--")
end
hold on 
end

What did I do wrong or miss?

[Cris LaPierre]

When you Submit, what are the results of the assessment tests?

• Did you create a plot with four lines?
• Did you plot lambda on the x-axis?
• Did you plot s on the y-axis?
• Did you use a dashed linestyle?
• Did you set hold to on?
• Did you include the code <= in the script?

[richard]

The entire code above to where I stated the if staement

results showed:

it showed a red x on the following

did you create a plot with four lines? x

did you plot lambda on x-axis? x

did you plot s on y-axis? x

did you use the dashed linestyle? x

did you set hold on?

did you include the code <=0? i got a gree check here

Answer 1

[Image Analyst]

I think you want dashed if it's below 0 and solid line if it's above 0, so something like

negativeIndexes = speed(v) <= 0; % A logical index vector.
% Plot negative values with dashed lines
plot(lambda(negativeIndexes), s(negativeIndexes), "--")
% Plot positive values with a solid line.
hold on;
plot(lambda(~negativeIndexes), s(~negativeIndexes), "-");

[Walter Roberson]

Not exactly, this would draw a line between non-adjacent parts.

Answer 2

[Cris LaPierre]

You appear to have replaced the for loop rather than adding the if statement to it.

If I take the code you have shared and add it correctly to the for loop, as shown in the Solution, it passes all assessment tests.

[richard]

How did i do that? I folloed the steps and even check the solution here and I keep getting the same results. So what can I do to correct this so I can contuine with 'the project. Otherwise I can't move forward.

[Cris LaPierre]

Share a screenshot with the code you are submitting and the assessment test results

[richard]

Never mind i finally found my mistake . I did not remove the end before I added the if statement. Thank you for you help

[Nursultan]

Hi! I have the same thing! The code seems to be correct, but for some reason it doesn't accept the job! What did you do?

[Cris LaPierre]

What are you seeing? If you code is the same as what is shown in 'See Solution', yet you are getting marked Incorrect, that sounds like what is reported here. Please follow the suggestions given in that post.

[Cris LaPierre]

Here is another post that sounds like what you are seeing. Please try the solution offered there (clear cache and cookies)