rounding a column vector

Question

Ankit Labh 2018-8-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/414825-rounding-a-column-vector

评论： Brent F 2021-7-23

I have a column vector with 8000 entries around temp (see array below).

temp=[5 50 150 180 200 220 240 250 260 265 270 272 274 275 275.5 276 277 278 279 279.5 280 280.5 281 281.5 282 284 286 288 290 295 300 310 320];     %temperatures [K]

I did the rounding up to one decimal places. Now I have numbers like 273.9 and 274.1 along with 274. I want to make all such 273.9 and 274.1 to 274, and wherever there is any number with .1 and .9, it should do the floor and ceil with that so that I always get an integer. 275.5 type numbers are the exception.

I tried to use this :

for i= 2:8351    
    while data(i,2)~=ceil(data(i,2))
        if data(i+1,2)== (data(i,2))+0.1
            data(i,2)=floor(data(i,2),0);
        elseif data(i-1,2)== (data(i,2))-0.1
            data(i,2)=ceil(data(i,2),0);
        elseif data(i+1,2)== (data(i,2))-0.1
            data(i,2)=ceil(data(i,2),0);
        elseif data(i-1,2)== (data(i,2))+0.1
            data(i,2)=floor(data(i,2),0);
        else
            data(i,2)=round(data(i,2),1);
        end
    end
end

Summary: There are 32 temperatures and around 8000 data points near those 32 temperatures. I want to go to one by one in each column and see if it has .1 or .9 and if so, round(or ceil or floor) it to the nearest integer.

Please help me in programming this.

Thanks.

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Ankit Labh 2018-8-14

Question is not specific to 274 but for all temp.

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Answer 1

Stephen23 2018-8-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/414825-rounding-a-column-vector#answer_332740

编辑：Stephen23 2018-8-14

在 MATLAB Online 中打开

This will round values from (X-1).9 to (X).1 to the integer X, otherwise leave the rounded values alone:

>> vec = 1:0.1:2
vec =
    1.00    1.10    1.20    1.30    1.40    1.50    1.60    1.70    1.80    1.90    2.00
>> new = round(vec*10)/10;
>> tmp = round(vec*4);
>> idx = mod(tmp,4)==0;
>> new(idx) = tmp(idx)/4
new =
    1.00    1.00    1.20    1.30    1.40    1.50    1.60    1.70    1.80    2.00    2.00

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Ankit Labh 2018-8-17

This works well !!! Thanks.

Brent F 2021-7-23

Clever. @Stephen Cobeldick used a multiplier + round (which rounds in both directions) to leave the middle untouched! I sense a general principle here...

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Answer 2

M 2018-8-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/414825-rounding-a-column-vector#answer_332739

编辑：M 2018-8-14

在 MATLAB Online 中打开

Try this:

temp=[273.9 274.1 274.5];
round(temp*2)/2
ans =
274.0000  274.0000  274.5000

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Ankit Labh 2018-8-14

编辑：Ankit Labh 2018-8-14

Thank you for your reply. There are 32 temperatures and around 8000 data points near to those 32 temperatures. I want to go to one by one in the column and see if it has .1 or .9 and if so, round(or ceil or floor) it to the nearest integer.

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