Xu Cui

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569 Stories by Xu Cui

Excel: how to fix a cell in formula?

Assume the formula is A1+B1, and you want to keep B1 fixed for other rows, then use A1 + $B$1
1 4 sec read

Convert images to matrix

Quite often you need to convert an image (or multiple images) to a MatLab matrix for further analysis and visualization (e.g. extracting time series, multivariate pattern analysis, etc). SPM provides handy functions for this: P = spm_select; % select
3 21 sec read

Wavelet Coherence

Wavelet transform coherence (WTC) is a method for analyzing the coherence and phase lag between two time series as a function of both time and frequency (Chang and Glover 2010). Here I played with it using the MatLab toolbox provided by Grinsted et a
18 1 min read

【转】静静的小河

离家不远处有一条静静的小河 闲暇时我和孩子总有一段时光在那儿度过 清清的河水静静地流淌 只偶有几头到河边吃草的老牛慢慢走过 柔顺飘逸的苔丝和水草为小河装点了绿意 一群群小鱼在上面散步跳舞唱歌 思绪像随
0 0 sec read

Standard deviation and standard error

Standard deviation (std): standard deviation of the sample Standard error, or standard error of the mean (sem), is the standard deviation of the mean. \(sem=std/\sqrt{N}\) Most errorbars in scientific publications refer to standard error. Quite often
0 22 sec read

Interview with David Shelly

David is an amazing person: he has published 5 papers in Nature and 1 in Science, two of which were published this year. Check out what he says in Peaya interview (click the photo below).
0 9 sec read

gmail is getting smarter

I noticed that gmail will remind you if you have something like “… is attached” in the email body but actually you don’t attach any files. This is very considerate.
0 6 sec read

Meaning of correlation coefficient

If variable X and Y has correlation 0.1, how much does it help to predict Y based on X? In the simplest binary case, the probability (p) to correctly predict Y based on X is a linear function of correlation (c), i.e. $$p=\frac{c+1}{2}$$ That means, a
1 14 sec read

Octopus Paul, hypothesis, p-Value and significance

Null hypothesis (H0): Octopus Paul doesn’t have the ability to predict. Or, the probability that he predicts correctly on each event is 1/2. Data: In 2010 World Cup, Octopus Paul correctly predicted the outcomes of 8 games out of 8 games. p-Val
0 16 sec read