Symbols of Mathematical Formulas in Papers

You should be talking about the hat matrix.

Meaning: an orthogonal projection matrix. For linear model Y=Xβ+e, E(e)=0, cov(e)=σ2I, matrix H? ... X(XTX)- 1XT is the projection matrix that orthogonally projects the observation vector y onto the subspace generated by the column vector of x ... ...

/link? URL = qjmtypjkrn 6 yv 9 dyp _ kHCremNF _ inapgeyklyfldh 5j 8 dejoudddgp 0 DSF 2 mjjql 9 svqxbptc 0 rqab 2 xeh kmk

Within 5 minutes

Is it difficult to pass the high school or junior high school teacher qualification examination?

How to cultivate junior high school students' logical thinking ability? Please tell me.

A hundred questions about mathematics in college entrance examination

How about prescribing in java?

How to add a math course with a little reading pen

Is the college entrance examination difficult in Jiangsu this year?

Why is it that after advanced filtering in excel tables, the filtering results are sorted by 1, 2, 3, 4, and the drop-down will not sort automatically? How to sort the filtered results?

Mathematics in Grade One is in the senior high school entrance examination.

Solution method of high school mathematical model