Please help me with matlab!

[kplonsky]

I am having a really hard time trying to answer this question.
"Create a normal distribution of temperatures (Gaussian distribution) with a
mean of 70F, and a standard deviation of 2 degrees, corresponding to 2
hours duration. You’ll need a temperature for each time value from 0 to
120 minutes."
I believe I have to use something like this "temp=randn(1,120)*2+70" but I think I am very far off. My matlab book doesn't show how to do Gaussian distribution.

Please help!!

 

[zorro]

I believe I have to use something like this "temp=randn(1,120)*2+70" but I think I am very far off.

Why do you think you are very far off? It's OK.
The only point is that if you need a sample for each time from 0 to 120 including start and stop, you would need 121 samples.
The question doesn't say nothing about it, but the samples generated in that way are idependent.
Regards

Z

 

[kplonsky]

Thank you for your help, the numbers looked weird in matlab.
temp=randn(1,121)*2+70
That should give me what I am looking for then right?

 

[zorro]

Yes, that should give you what you are looking for.
Why the numbers look weird?
Regards

Z

 

[kplonsky]

Thank you for your assistance on that problem. I ran into another now...

The distance a projectile travels when fired at an angle θ is a function of time and can be divided into horizontal and vertical distances :
Ht= t
*Vo*cos(θ)
Vt=t*Vo*sin(θ) – ½gt
2
where:
Ht is the distance traveled in the x direction
Vt is the distance traveled in the y direction
Vo is the initial velocity
g is the acceleration due to gravity, 9.8m/s
t is the time

a. For the projectile just described and fired at an initial velocity of 100 m/s and a launch angle of pi/4, find the distance traveled both horizontally and vertically ( in the x and y directions ) for times from 0 to 20 seconds. Graph horizontal distance versus time on one plot, and in a new figure window plot vertical distance versus time (time on x – axis). Don’t forget the title and the axis labels.

Vo=100; %m/s
time=(0:20); %Seconds
g=9.8; %Gravity m/s^2
Ht=time.*Vo*cos(45);
Vt=time.*Vo*sin(45)-(1/2)*g.*t^2;

I was having a hard time using radians in Matlab so I switched it to degrees instead. Sorry for this huge mess on the forum, I am struggling with this program. I don't think I put the equation into Matlab correctly because the plots all come out to be the same.

 

[zorro]

Hi,

1) radians or degrees:

sin(), cos(), etc. use arguments in radians.
sind(), cosd(), etc. use arguments in degrees.
So you have to correct your code.


2) For converting angles from degrees in radians and vece versa:

angle_in_radians = angle_in_degrees * pi/180;

angle_in_degrees = angle_in_radians * 180/pi;


3) I recommend to put this line at the beginning:

thetaD = 45;

ant then use thetaD instead of a particular value.


4) In the line

Vt=time.*Vo*sin(45)-(1/2)*g.*t^2;

what is t? It should be like this:

Vt=time.*Vo*sind(thetaD)-(1/2)*g*time.^2;


Regards

Z