I have a function file, I want to input an array and evaluate each cell in that array. How do I alter my function file to do this?

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Marco
Marco 2013-4-7
function x=isoddm(a)
if isnan(a)==1
x=-1;
elseif mod(a,2)==0.5
x=-1;
elseif mod(a,2)==1.5
x=-1;
elseif mod(a,2)==0
x=0;
elseif mod(a,2)==1
x=1;
else
x=nan;
end
The purpose of this function is to see whether an array element is an integer or not and if it is, is it an even or odd number. The problem I am having is that it cannot evaluate each cell in an array individually.

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Marco
Marco 2013-4-7
编辑：Walter Roberson 2013-4-7
I have found a long and painful answer to my own question that does not involve WR's suggestion. I remade x into x1, x2, and x3. Here is the nested if loop for x1, which determines if a(1) is a real number then proceeds to determine if it is nan or not, then an integer, then even or odd;
function [x1,x2,x3]=isoddm3(a)
% For x1
if isreal(a(1))==0
x1=-1;
elseif isreal(a(1))==1
if isnan(a(1))==1
x1=-1;
elseif mod(a(1),2)==0.5cle
x1=-1;
elseif mod(a(1),2)==1.5
x1=-1;
elseif mod(a(1),2)==0
x1=0;
elseif mod(a(1),2)==1
x1=1;
end
end
It goes on to calculate x2 and x3, which are exactly the same steps for x1 but replaced with x2 or x3. At the end I had to produce a psuedo-array for x using fprintf; fprintf('x=[%g\n %g\n\n %g\n\n\n] Ignore ans',x1,x2,x3) because the answer (ans) would only display x1.

更多回答（1 个）

Walter Roberson
Walter Roberson 2013-4-7
Use logical indexing. For example,
x = -1 * ones(size(a));
x( mod(a,b) == c ) = d;
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Marco
Marco 2013-4-7
I'm not sure what you mean, and I've tried your first suggestion but it resulted in NaN NaN NaN, not the answer I expect for the first two elements, and I'm confused by the second, what do b and c represent?
Walter Roberson
Walter Roberson 2013-4-7
There is no such thing as an "if loop". There are "for loop" and "while loop" and "if statement". The body of an "if" executes either 0 times (for false) or 1 time (for true); loops are for executing the body multiple times.
In my example, b, c, and d are values you will need to determine for your purposes. For example in one case, "b" might be 2. I deliberately did not give examples of what values you would use for b, c, and d because most of your original code was wrong (and still is, in your code that you Accepted.)
You basically have 3 cases: one case is all the situations that produce -1, one case is the situations that produce 0, and one case is the situations that produce 1. Your series of "if" statements can be replaced by an initialization of x, followed by three statements of the form
x( mod(a,b) == c ) = d;
with appropriately chosen "b", "c", and "d" (e.g., in one case, d would be -1, in another it would be 0, in the third it would be 1.)
To give an example, if you were required to give -3 for numbers of the form of 7x+5, then
x( mod(a, 7) == 5 ) = -3;

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