Info

此问题已关闭。请重新打开它进行编辑或回答。

您正在关注此问题

您将在关注的内容源中看到更新。
您可能会收到电子邮件，具体取决于您的通信预设项。

How to subtract from a vector, have it return a value of zero if the answer is less than zero, and then tell me how much was subtracted?

2 次查看（过去 30 天）

显示更早的评论

Brett Baxter 2020-9-15

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t

⋮

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t

关闭： MATLAB Answer Bot 2021-8-20

在 MATLAB Online 中打开

I essentially need to write a function like this:

x=[1, 2 3]
y= 2
x(1) - y
if x(1)<0
    totalsubtracted = y +x(1)
x(1)=0
else
    totalsubtracted = x(1)-y
end

But without conditionals. How do I do this?

回答（1 个）

madhan ravi 2020-9-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#answer_495037

⋮

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#answer_495037

在 MATLAB Online 中打开

totalsubtracted = (x(1) < 0) * (y + x(1)) + (x(1) > 0) * (- y + x(1)) % ?

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010503

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010503

That works only if the result is negative. I would need it to also work if the result is positive.

Like if x(1)>2 and y = 2

this would mean that x(1) = x(1)-y would give an output that was greater than or equal to 1, which is positive. When I run that script, it doesn't give me the total subtracted as 2 like it should

madhan ravi 2020-9-15

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010509

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010509

在 MATLAB Online 中打开

x = [1, 2, 3]
y = 2
% Desired result?

Brett Baxter 2020-9-15

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010521

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010521

编辑：Brett Baxter 2020-9-15

在 MATLAB Online 中打开

Let me be a little more specific

Imagine I had a vector of some numbers like

x =[55 65 70]

and I wanted to subtract some input value from the first number in this vector, like so

y = 65
x(1) = x(1) - y

This would produce the following result under normal circumstances

x = -10 65 70

Now what I need matlab to do: if x(1) is a negative number after subtraction, then x(1) needs to be set to 0, like so

x = 0 65 70

Then, I need matlab to tell me how much was subtracted from x(1). If the number returned in x(1) is negative after subtraction, I need it to tell me how much was subtracted from x(1) barring any numbers less than 0. So, in this case, I want it to tell me

totalsubtracted = 55

But, if x(1) is not negative, I need it to tell me how much it subtracted. Like the following

x = [70 65 70]
y = 65
x(1) = x(1) - y
x = 5 65 70
totalsubtracted = 65

does this make sense? I need to do this WITHOUT using any conditionals

madhan ravi 2020-9-15

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010530

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010530

编辑：madhan ravi 2020-9-15

在 MATLAB Online 中打开

“ WITHOUT using any conditionals”

Isn’t that your homework?

 x(1) = x(1) * (x(1) > 0)
 totalsubtracted = y

Brett Baxter 2020-9-15

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010536

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010536

It isn't all of my homework, it's only a specific part that I need for a later part. I've run into this problem because I don't know how else to get this without using conditionals. The numbers I have in my question are only as an example of what I'm trying to accomplish.

Brett Baxter 2020-9-15

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010557

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010557

编辑：Brett Baxter 2020-9-15

在 MATLAB Online 中打开

Yes, that works, but if the resulting value is negative, y does not equal total subtracted. I know it sounds silly but if the resulting value is negative, then the total subtracted needs to come back as the value subtracted from x(1) up until it became less than 0

like I said earlier

x(1) = 1
y = 2
x(1) = x(1) - y
%this would then return a vector where
x(1) = -1

Yes, the total subtracted would be the value of y, but I need matlab to tell me how much was subtracted BEFORE the value went below 0

so in this case

%I'm looking for this answer
totalsubtracted = 1
%NOT this answer
totalsubtracted = 2

I need this to work for both cases, where x(1) > 0 and x(1) < 0 without any conditionals

madhan ravi 2020-9-15

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010563

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010563

Ok ,so wait for the response. Don’t ask the same question a billion times before responding here.

Brett Baxter 2020-9-15

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010569

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594259-how-to-subtract-from-a-vector-have-it-return-a-value-of-zero-if-the-answer-is-less-than-zero-and-t#comment_1010569