generation of data plot using an equation

4 次查看（过去 30 天）
Hirak
Hirak 2013-12-18
评论： Niklas Nylén 2013-12-19
Hi Friends, I am a newbie in this world. Major of my work consists of generation of data plot. Recently I am need for a code in which I can vary r_shell for a fixed value of r_core to find out g from the given equation:
  • g=[(r_core+r_shell)^3-r_shell^3]/(r_core+r_shell)^3
  • The range of r_shell is 0 to 5.2 with gap 0.26. In each case, the value of r_core is fixed at 5. Plot should be r_shell in x-axis and g in y-axis.I also need the data in tabulated form.My code was:
if true
clear all;
close all;
dbstop if error;
r_shell=vertcat(0:.26:5.2);
r_core=5;
for i=0:length(r_shell);
a = (r_core+i).^ (3)-(i).^ (3);
g= a/(r_core+i).^3;
end
temp=[i;g]';
save('temp','-ascii')
figure
plot(temp(:,1),temp(:,2));
xlabel('Shell thickness(nm)')
ylabel('Murray g factor');
save('diel.tab','temp','-ascii') % code end
I wrote the code but due to my lack of knowledge it remain failed to made it. Please suggest me. I am in deep need of it. Thank you all and Merry Christmas for you and family. Hirak

请先登录，再回答此问题。

采纳的回答

Hirak
Hirak 2013-12-18
Thank you Niklas. It worked nicely. Now, if I want to vary r_core also, say, for the spread 1:0.1:10, and make a three dimensional plot,what should I do? I want to learn MATLAB. From where should I start? There is no one here to teach me MATLAB. Please suggest me. With warm regards, Hirak.

更多回答（1 个）

Niklas Nylén
Niklas Nylén 2013-12-18
I can see a few issues in your code:
The use of vertcat when defining r_shell seems unnecessary, this should give the same result:
r_shell=0:.26:5.2;
Matlab indexes start at 1, not 0, and you also use the counting variable i instead of the value r_shell(i), but in this case a for loop is unnecessary. A matrix operation is faster:
g=((r_core+r_shell).^3-r_shell.^3)./(r_core+r_shell).^3
To plot the data:
figure
plot(r_shell, g);
xlabel('Shell thickness(nm)')
ylabel('Murray g factor');
And save the data in an ascii file
data = [r_shell; g]:
save('diel.tab','tmp','-ascii')
  2 个评论
Hirak
Hirak 2013-12-19
Thank you Niklas. It worked nicely. Now, if I want to vary r_core also, say, for the spread 1:0.1:10, and make a three dimensional plot,what should I do? I want to learn MATLAB. From where should I start? There is no one here to teach me MATLAB. Please suggest me. With warm regards, Hirak.
Niklas Nylén
Niklas Nylén 2013-12-19
What you will want to do is to create two vectors where all combinations of the two original vectors are present. I will use variable names x and y in this example with some limited amount of data for readability.
Step 1: Create the original vectors (this is r_shell and r_core in your case)
>> x = 1:0.5:2;
>> y = 8:1:10;
Step 2: Create all combinations of the two vectors x and y by using the function meshgrid
>> [x1,y1] = meshgrid(x,y)
This will create two matrices where all combinations are available
x1 = 1 1.5 2
1 1.5 2
1 1.5 2
y1 = 8 8 8
9 9 9
10 10 10
Although you can use these matrices as direct inputs to your calculation, for future plotting it would be nice to have them as vectors instead.
>> x1 = x1(:)
>> y1 = y1(:)
x1 = 1 1 1 1.5 1.5 1.5 2 2 2
y1 = 8 9 10 8 9 10 8 9 10
As you can see, if you combine the elements with the same index in the two vectors, you get all possible combinations. Now you can use the vectors in a calculation, for example
>> z = (x1 + y1.^x1)./x1
z = 9.00 10.00 11.00 16.08 19.00 22.08 33.00 41.50 51.00
To plot the 3d data, use the command plot3
>> figure
>> plot3(x1,y1,z,'.')
>> grid on
It looks like the answer you accepted above was your own response, please click accept on my answer instead.
As for learning matlab, I would suggest either searching online for some small projects that you can create. There are also a number of beginner tutorials available.

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Resizing and Reshaping Matrices 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by