In MATLAB (or more generally) if I wanted something to happen only, for example, every 50 iterations of a for loop how could I do this better than below? That is to not write out every possible value of +50. Thanks.
for i = 1:1060;
if i = 50 || 100 || 150 || ... || 1050
randi(i); % for example, just do something
end;
end;
What you want is
if mod(i, 50) == 0
do something
What you want is
for i = 0:50:1050
do_stuff(i);
end
unless, it is unclear from your question, if the previous answer is what you really want, which you might need in the case that looks like this
for i = 1:1060
if mod(i, 50) == 0
do_something(i)
end
do_something_else(i)
end
Cheers,--
Related
I'm trying to evaluate the performance of these two loop method, I tried number from 0 to 99999 using for in and while loop clause.
for i in 0..<s.count - 9 {
print("\(i)")
}
var j = 0
while j < s.count - 9 {
print("\(j)")
j = j+1
}
In both loop, will print the current number and add number by 1 until it reaches 99999.
Turns out that for in clause use 0.91 to go through every number, at same time while take much much much longer time (around 80.8).
I searched on Internet and documents, but cannot figure out why.
What cause this huge performance difference?
I'm writing a program to play blackjack and one of the functions calculates the score. It takes in an input which is a structure array of cards and one of the attributes is value (for an ace the value is 11). My function is supposed to determine if the total of the values is over 21 and if 1 of the cards is an ace, then the ace's value is changed to 1. Can anyone help me figure this out please?
for index=1:length(input)
if(input(input).value == 11)
input(index).value = 1;
end;
end;
You're not actually summing the cards in your original snippet. You also seem to have a typo in input(input), I think this should be input(index). If you wanted to do it with a for loop like you have, you'd do something like this:
total = 0;
for index=1:length(input)
if(input(index).value == 11)
input(index).value = 1;
end;
total = total + input(index);
end;
The more MATLAB way of doing things would be to avoid loops by using the sum in-built command.
Sorry for pretty basic question.
Just starting out. Using flowgorithm to write code that gives out a calculation of exponential numbers.
The code to do it is:
function exponential(base, power) {
var answer;
answer = 1;
var i;
for (i = 1 ; i <= power ; i+= 1) {
answer = answer * base;
}
return answer;
f
then it loops up to the number of power. And i just understand that in the flowgorithm chart but i dont understand the code for it.
what does each section of the for statement mean?
i = 1 to power, i just need help understanding how it is written? What is the 1+= 1 bit?
Thanks.
The exponential function will take in 2 parameters, base and power.
You can create this function and call (fire) it when ever it is needed like so exponential(2,4).
The for (i = 1; 1 <= power; i+=1) is somewhat of an ugly for loop.
for loops traditionaly take three parameters. The first parameter in this case i =1 is the assignment parameter, the next one 1 <= power is the valadation parameter. So if we call the function like so...exponential(2,4) is i less than 4? The next parameter is an increment/decrement parameter. but this doesnt get executed until the code inside the for loop gets executed. Once the code inside the for loop is executed then this variable i adds 1 to itself so it is now 2. This is usefull because once i is no longer less than or equal to power it will exit the for loop. So in the case of exponential(2,4) once the code inside this for loop is ran 5 times it will exit the for loop because 6 > 5.
So if we look at a variable answer, we can see that before this for loop was called answer was equal to 1. After the first iteration of this for loop answer = answer times base. In the case of exponential(2,4) then answer equals 1 times 2, now answer =2. But we have only looped through the foor loop once , and like i said a for loop goes like (assignment, validator, "code inside the foor loop". then back up to increment/decrement). So since we to loop through this for loop 5 times in the case of exponential(2,4) it will look like so.
exponential(2,4)
answer = 1 * 2
now answer = 2
answer = 2 * 2
now answer = 4
answer = 4 * 2
now answer = 8
answer = 8 * 2
now answer = 16
answer = 16 * 2
now answer = 32
So if we could say... var int ans = exponential(2,4)
Then ans would equal 32 hence, the return answer; at the last line of your code.
This is quite a simple issue, but I've been struggling with it. sortedd and sortedfinal_d are 8 x 1000 Matrices and I am using the loop below to check if any of the elements in sortedfinal_d lies between two consecutive elements of sortedd, in terms of magnitude. I'm doing this along each row. overall_p is a 8 x 1000 Matrix as well, but at the end of this process I end up having final_p as a Matrix of Zeros. I don't know why this is.
for k=2:1000
for s=1:1000
for j=1:8
if sortedd(j,k) > sortedfinal_d(j,s) && sortedfinal_d(j,s) > sortedd(j,k-1)
final_p(j,s) = overall_p(j,k);
end
end
end
end
EDIT: Added data for the inputs as shown below:
sortedd (first four columns) =
0.219977361620113 0.219996752039812 0.220344444223787 0.220593274018691
0.272807483153955 0.273682693068593 0.273846498221277 0.274060049642900
0.327201460264565 0.327375792227635 0.327572790857546 0.327856448530021
0.380389118311424 0.380845274148177 0.380893687870765 0.381015090963159
0.434832574575088 0.434860658844550 0.435021604722982 0.435119929919457
0.487119089589798 0.488128501559782 0.488207451439073 0.488430455768512
0.540652551559395 0.541303305046034 0.542195194863130 0.542234381085921
0.595254195563241 0.595296064375604 0.595376090156252 0.595377962767971
sortedfinal_d =
0.182086792394190 0.182406508309366 0.182406508309366 0.182808976400818
0.233058295607543 0.233058295607543 0.233158455616954 0.233158455616954
0.286243848617693 0.286357973626582 0.286918095670684 0.287393171241241
0.336938335090164 0.336938335090164 0.337094505106945 0.337669618738100
0.390287818652551 0.390567879874952 0.390567879874952 0.390670502700602
0.446995120903824 0.447270251510681 0.447452123072880 0.447597175111267
0.501060785098551 0.501060785098551 0.501060785098551 0.501060785098551
0.551311219045087 0.551463923687602 0.551463923687602 0.551653815175502
Thanks a lot
Do you have to use loops to accomplish this?
matching_d = sortedfinal_d(:,1:end-1) < sortedd(:,2:end) ...
& sortedd(:,2:end) < sortedfinal_d(:,2:end);
final_p(matching_d) = overall_p(matching_d);
If you can show us a small sample input (say, 1x5 versions of sortedd and sortedfinal_d) and output (the corresponding matching_d) it would be easier for us to help troubleshoot.
If i set your matrices to random numbers, final_p does return some numbers.
So your code works as is. Post your dataset or at least describe the dataset in some detail, this will make it much easier to diagnose the problem.
I have reduced 1000 down to 10 and re-ordered the iteration variables to i, j, k to make it easier to follow:
sortedd = rand(8, 10);
sortedfinal_d = rand(8, 10);
overall_p = rand(8, 10);
for i=2:10
for j=1:10
for k=1:8
if sortedd(k,i) > sortedfinal_d(k,j) && sortedfinal_d(k,j) > sortedd(k,i-1)
final_p(k,j) = overall_p(k,i);
end
end
end
end
final_p
for s=1:length(C_tem)
for w=1:length(C_tem{s})
if (abs(C_tem{s}{w}) >= 0)
C_tem{s}{w} = 1;
else
C_tem{s}{w} = 0;
end
end
end
I am trying to set the values larger than 0 to 1, and if less or equal to 0, but for some reason this doesn't work.
I'm new in matlab, and I really need the help if possible. Thank you in advance..
i havn't worked on matlab much but this part of code feels suspicious -
if (abs(C_tem{s}{w}) >= 0)
C_tem{s}{w} = 1;
else
C_tem{s}{w} = 0;
end
Why are you doing abs here? I think it will remove sign from number. Code should be something like this-
if (C_tem{s}{w} > 0) //I have removed abs and >= is replaced with >
C_tem{s}{w} = 1;
else
C_tem{s}{w} = 0;
end
abs(x)>=0 is true for all values of x. The simple answer is to remove the abs. The more complete answer follows up on Dan's comment. The cell array is unnecessary at the inner level. If you instead had a cell array of regular arrays, then you could do this for the entire block of code.
for s=1:length(C_tem)
C_tem{s} = (C_tem{s} >= 0);
end
Two things to notice: comparison operators are vectorized, meaning they return a matrix of the same size as the input, thus comparing all values at once. And, the output of the operator is 1 where true and 0 where false.
Also look at the builtin function sign to see if that's closer to what you want to do.