If statement correction help

2 次查看（过去 30 天）
Tony Chan
Tony Chan 2019-3-11
编辑： per isakson 2019-3-11
Hi I am trying to write an if statement. What I need is to create an array of 1000 random variables from -1 to 0 and 1/2 to 1. My algorithm is if the number in that element is less than 0 and greater than 0.5, move onto the next, if not repeat but doesn't not seem to work when I check the resulting array. Sorry if this may be rudimentary but so far I wrote:
X1 = zeros(1, 1e3);
for i=1:numel(X1);
X1(i)=-1+(2)*rand(1);
if X1(i) < 0 & X1(i) > 0.5;
i=i+1;
else
i=i;
end
end
Thank you so much, I appreciate the help.
  2 个评论
madhan ravi
madhan ravi 2019-3-11
编辑：madhan ravi 2019-3-11
flip the direction of relational operators and use && instead of &
Walter Roberson
Walter Roberson 2019-3-11
It is not possible for a number to be sumultaneously less than 0 and greater than 1/2 . You might want to use | instead of & or you might want to use > and < instead of < and >
Note that any change you make to a loop control variable such as i inside the loop will be ignored on the next iteration of the loop. You cannot cause a particular for iteration to repeat by adjusting the loop control variable. Consider using while

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回答（1 个）

per isakson
per isakson 2019-3-11
编辑：per isakson 2019-3-11
"I need is to create an array of 1000 random variables from -1 to 0 and 1/2 to 1"
Another approach
>> X1 = rand(1,1e3)*1.5 - 1;
>> X1(X1>0) = X1(X1>0)+0.5;
>> plot(X1,'.')
or to get the "same" number of elements in each interval
>> X1 = rand(1,1e3)*2 - 1;
>> X1(X1>0) = X1(X1>0)/2 + 0.5;
>> plot(X1,'.')

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