# dividing defined variable by named variable

6 views (last 30 days)
Liam Bates on 28 Sep 2022
Commented: Image Analyst on 28 Sep 2022
everytime i try to divide a defined variable by a calculated variable, it only outputs one number multiple times. What syntax am i missing?
d=1:.2:3;
a=sqrt((d.^2)*(3^2));
Y=d./a
Stephen23 on 28 Sep 2022
Edited: Stephen23 on 28 Sep 2022
" it only outputs one number multiple times."
Because that is the correct result for your code, which is equivalent to d./(3*d)
"What syntax am i missing?"
Because you did not state the expected output nor what you are trying to achieve, we cannot guess the syntax that is required to achieve an unstated goal.

Image Analyst on 28 Sep 2022
Well yeah. Just look at the numbers:
d = 1 : 0.2 : 3
d = 1×11
1.0000 1.2000 1.4000 1.6000 1.8000 2.0000 2.2000 2.4000 2.6000 2.8000 3.0000
a = sqrt((d.^2)*(3^2))
a = 1×11
3.0000 3.6000 4.2000 4.8000 5.4000 6.0000 6.6000 7.2000 7.8000 8.4000 9.0000
Y = d ./ a
Y = 1×11
0.3333 0.3333 0.3333 0.3333 0.3333 0.3333 0.3333 0.3333 0.3333 0.3333 0.3333
They all look right to me. Exactly what output numbers did you expect? Tell me which element of Y it got wrong and should be a different number.
Image Analyst on 28 Sep 2022
You can define "a" differently then, like perhaps add noise
d = 1 : 0.2 : 3
d = 1×11
1.0000 1.2000 1.4000 1.6000 1.8000 2.0000 2.2000 2.4000 2.6000 2.8000 3.0000
a = sqrt((d.^2)*(3^2)) + rand(size(d))
a = 1×11
3.3071 4.0240 4.6150 5.2096 5.6304 6.3306 7.5081 8.0647 7.8299 8.5545 9.7844
Y = d ./ a
Y = 1×11
0.3024 0.2982 0.3034 0.3071 0.3197 0.3159 0.2930 0.2976 0.3321 0.3273 0.3066

Walter Roberson on 28 Sep 2022
a=sqrt((d.^2)*(3^2))
3^2 is 9 so inside the sqrt() you have 9*d^2. sqrt() of that is sqrt(9)*sqrt(d^2). For positive d that is 3*d
Y = d ./ a
So you have d divided by 3*d. For non-zero d that is going to be 1/3 no matter what the positive value of d is. For negative d you would get -1/3. For 0 you get nan.

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