nothing assing to my variable that is in if statement

hello I wrote a code and it has 5 x and 3 y .

and with different conditions of x, a value should assign to y , but when i run my code in if statement no value assign to y and I wrote y(:,i) = Gt_new(1)

what should i do ?

thank you

my code is

clc; clear all ;close all
warning off

x1 = randi([0,5],1,10);


x = zeros(1,5);
P = 50;
for i = 1:length(x1)/2
    x(:,i) = x1(:,2*i) - x1(:,(2*i)-1);
end

xmin = min(x);
xmax = max(x);
Gt = 40
dx = 10;
Gt_new = Gt + [+dx 0 -dx];
y1 = find(x<0)
y2 = find(x == 0)
y3 = find(x>0)

y = zeros(1,5);
for i = 1:length(x)/2 
   if x < 0 
       y(:,i) = Gt_new(1)
   end
end

Answer 1

[Mathieu NOE]

hello

you need to index x in the for loop

for i = 1:length(x)/2
   if x(i) < 0 % here
       y(:,i) = Gt_new(1)
   end
end

[arash rad]

Hi thank you for your answer

I did this but yet nothing happen

[Mathieu NOE]

hello again

your original code gives y = 0 0 0 0 0

the modified code gives another output : y = 0 50 0 0 0

(depends what randi generated in first insyance)

x1 = randi([0,5],1,10);
x = zeros(1,5);
P = 50;
for i = 1:length(x1)/2
    x(:,i) = x1(:,2*i) - x1(:,(2*i)-1);
end
xmin = min(x);
xmax = max(x);
Gt = 40

Gt = 40

dx = 10;
Gt_new = Gt + [+dx 0 -dx];
y1 = find(x<0)

y1 = 1×4

1 3 4 5

y2 = find(x == 0)

y2 =

  1×0 empty double row vector

y3 = find(x>0)

y3 = 2

y = zeros(1,5);
for i = 1:length(x)/2 
   if x(i) < 0 
       y(:,i) = Gt_new(1)
   end
end

y = 1×5

50 0 0 0 0

y

y = 1×5

50 0 0 0 0