i have a problem rounding a loop

so if i write a loop that and it gives me a answer of .0215243225 you know just a huge number but i wanted to round it to the .0001, .001, .01. how would i do that i m using a for statment for a loop

[John D'Errico]

What is huge about the number you gave? I guess, compared to avogadro's number, it is huge. ;-)

But why in any remote scenario would you use a loop to do this, instead of using roundn? Why would you use a loop in any case?

Ok, this will do...

for loopindex = 1:1
  x = roundn(x,2);
end

But it seems a bit of overkill.

Seriously, if this is not homework, then you need to answer why you would possibly not use roundn.

If it is homework, then you need to answer why we should be doing your homework for you, and even given that, why we would use a loop anyway.

[Raul Castillo]

i dont think you understood me lol (nice pun btw) but i am writing a code

with a loop because loops are great to use. on the other hand if i want to round any output up then how would i do that. so basically what im saying is that if i using a loop how can i get the output and round it to a specific decimal such as.01,.001,.0001.

[John D'Errico]

I'm still a little confused. Let me give an example. I'll compute a simple result, doing it in a loop. Then I'll round the result to 2 decimal places, still inside the loop.

n = 5;
result = zeros(1,n); % preallocate vectors like this
for i = 1:n
   result(i) = sin(i);
   % rounding it, to 2 digits after the decimal
   result(i) = round(result(i),2);
end

result
result =
         0.84         0.91         0.14        -0.76        -0.96

Admittedly, I never needed to use a loop to do any of this, but to show it gave the desired result...

[1:5;sin(1:5);round(sin(1:5),2)]
ans =
            1            2            3            4            5
      0.84147       0.9093      0.14112      -0.7568     -0.95892
         0.84         0.91         0.14        -0.76        -0.96

As you can see, the round operation inside the loop did what it is supposed to do.

But I have a very funny feeling that this is not what you are really asking.

[Raul Castillo]

no lol its okay thank you for the help sir i appreciate it!

[Shubham Gupta]

Do you want to round the value to significant digits, which will change in a loop? For e.g.

a_answer= .0215243225;
for i = 2:5
    output = round(a_answer,i)
end

% You will get output
output =

         0.02


output =

        0.022


output =

       0.0215


output =

      0.02152

It's basically the same method as mentioned by John, only instead of looping on values I looped it for significant digits.

[Steven Lord]

Shubham Gupta,

You can do that without manually adjusting the number of digits by specifying the 'significant' option in your call to round.

>> a_answer= .0215243225;
>> round(a_answer, 3, 'significant')
ans =
                    0.0215
                    
>> b = pi/1000;
>> round(b, 3, 'significant')
ans =
                   0.00314

>> round(b, 5)
ans =
                   0.00314