the problem of using 'case'

i want to use a loop of omega and when the omega has diffreent value ,the m0,m1,m2...have the different value,so in the loop i use the 'case' as this

for omega=0.1:0.1:2;
  
switch omega

case 0.100000;


m0=0.031949;
m1=3.141268;
m2=6.283023;
m3=9.424670;
m4=12.566289;
m5=15.707898;
m6=18.849502;
m7=21.991102;
m8=25.132701;
m9=28.274298;
m10=31.415894;


case 0.200000;


m0=0.063931;
m1=3.140293;
m2=6.282536;
m3=9.424345;
m4=12.566046;
m5=15.707703;
m6=18.849339;
m7=21.990963;
m8=25.132579;
m9=28.274190;
m10=31.415797;

and there are still some codes,but in the result,when omega=0.2,it still use the m0,m1,m2...of case 0.100000;

so when i change it as

case abs(omega-0.200000)<0.01;

it still has the problem,and why,thanks a lot!!!

[Stephen23]

Numbering variable names is a sign that you are doing something wrong. You should simply store all of those scalar numerics in one numeric array.

Answer 1

[Stephen23]

Your first (inadvisable, numerically fragile, should-be-avoided) concept works for me:

for omega = 0.1:0.1:2;
	switch omega
	case 0.1
		disp('one')
	case 0.2
		disp('two')
	end
end

displays this in the command window:

one
two

Because of floating pont error in those numbers, this would be an extremely unreliable way to write code. Do NOT do this!

Your second method can be done quite easily, by simply thinking about the actual case value that you actually want switch to compare (hint: your case conditions are equal to true or false, but omega is not equal to true or false):

for omega = 0.1:0.1:2;
	switch true % this is the value for a valid CASE.
	case abs(omega-0.1)<0.01;
		disp('one')
	case abs(omega-0.2)<0.01;
		disp('two')
	end
end

displays this in the command window:

one
two

[dcydhb dcydhb]

i have accepted as it is wonderful and i was curious that

	switch true % this is the value for a valid CASE.
	case abs(omega-0.1)<0.01;
		disp('one')

you must use the

switch true % this is the value for a valid CASE.

rather than

switch omega

why?

[Walter Roberson]

When you use

switch numeric_value
    case another_numeric_value

then the test is

if numeric_value == another_numeric_value

So let us follow that through with your proposed version with switch omega:

if omega == (abs(omega-0.1) < 0.01)
    

The right hand side is a logical value, false or true, convertable to numeric 0 or 1, and you want to compare that to omega. That can only possibly succeed if omega is 0 or 1 . In the case where omega is 1 then abs(1-0.1) is 0.9 and < 0.01 of that is false. In the case where omega is 0, then abs(0-0.1) is 0.1 and < 0.01 of that is false. Therefore switch omega cannot work.

Let us instead follow through with switch true:

if true == (abs(omega-0.1) < 0.01)

which can be true if omega is in the range approximately 0.1-0.01 to 0.1+0.01

[dcydhb dcydhb]

great explanation and thank you all a lot!!!