- just the image
- the MATLAB figure file, but not the underlying data that made the plot
- the underlying data
Convert negative values to positive values in the graph
49 次查看(过去 30 天)
显示 更早的评论
I have this graph:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1348899/image.jpeg)
The question is, can I convert those negative values to positive? I mean, so that all those spikes in the graph will go upwards instead of go downwards. I mean it will go something like this:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1348904/image.png)
Thank you.
0 个评论
采纳的回答
the cyclist
2023-4-7
Yes, but the answer depends on what exactly you have. Do you have
If you have the underlying data, just use abs to take the absolute value of the variable on the y axis, and re-plot.
4 个评论
the cyclist
2023-4-8
If all you want to do is for your negative values to be positive, then abs() obviously does the job.
tt = edfread('example.edf');
info = edfinfo('example.edf');
fs = info.NumSamples/seconds(info.DataRecordDuration);
recnum = 5;
signum = 2;
t = (0:info.NumSamples(signum)-1)/fs(signum);
y = tt.(signum){recnum};
plot(t,abs(y)) % All I did was add abs() here
更多回答(1 个)
埃博拉酱
2023-4-8
编辑:埃博拉酱
2023-4-8
It depends on the meaning of negative values and how they are generated.
From your graph, your data appears to be oscillating with a mean of 0, which may be due to normalization. In this case, negative values make sense, and it is recommended to use a method similar to Data-min(Data(:)) so that the minimum value becomes 0.
If you want to calculate a statistic that is not possible to be negative by definition, such as power, you should usually square the data.
If you are very sure that negative values are meaningless error values, it is recommended to use interpolation to change negative values to the average of positive values on both sides.
I can't quite agree with @the cyclist. When dealing with natural measurements like EEG, it rarely makes sense to use abs because it is continuous but non-differentiable at zero, a feature that is too weird in the macroscopic physical world.
0 个评论
另请参阅
类别
在 Help Center 和 File Exchange 中查找有关 Biomedical Signal Processing 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!