scRNA-seq: Dimension reduction (PCA, tSNE, UMAP)

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We are now done with the pre-processing of the data. It’s time to talk about dimension reduction.
We won’t go through the mathematical details, but instead aim for the intuition of how dimensional reduction methods (PCA, tSNE, UMAP) work. We want to learn how to reduce dimensions and visualise our data. We also learn how to select the principal components for the clustering step.

01:57 PCA
08:50 tSNE and UMAP for visualisation
10:05 tSNE
11:23 UMAP

We also recommend the excellent StatQuest videos explaining PCA, such as:
or:

Finally, the image on the slide "Other dimension reduction methods: used later for visualisation" is by Shigeo Takahashi, Issei Fujishiro, and Masato Okada, "Applying Manifold Learning to Plotting Approximate Contour Trees," IEEE Transactions on Visualization and Computer Graphics (Proceedings of IEEE Visualization / Information Visualization 2009), Vol. 15, No. 6, pp. 1185-1192, 2009.
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i'm biologist and now i get the main idea of this topic :) thanks a lot for this, now i have to move to the explanation of Paulo about tSNE and UMAP

gama
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If we use 5-15 PCs, then how do we represent all of these dimensions visually? I understand that with 2-3 dimensions we can put the data onto a single graph, so with this number of dimensions would we have to draw out many different graphs during the analysis stage? How would we present all of these dimensions in a research project?

singhh
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Can I ask how did you draw the heatmap for each PC, what is exactly shown in the heatmap each PC ? I am really confused. Thank you a lot.

jieyang
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You took that tSNE slide from StatQuest

conduit
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Can I get your code, for the entire purpose?

onkarmulay
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