Quasi Concave and Quasi Convex Functions

[@gurpreetsingh2301]

The quote in Punjabi hanging on the wall translates to: "If we love our work, work turns into passion". Can really sense the passion in this helpful explanation of hers!

[@komalrani1856]

This was an amazing lecture. Believe me there are very few people who can really make you understand this topic. Being a vague topic people just keep learning it without having clear knowledge about it. I thank you for this. You are a great teacher. May God bless you with good fortune Please make more videos

[@junxiliu4334]

She is so beautiful and enthusiastic, and explains the concepts so clearly and vividly. Though the environment is not so good, she is a true teacher shining.

[@userbee156]

Wow. Searched the entire google and searched the entire youtube for this explanation and all those just confused me until i came across your video. Just wow. God bless dear. Great explanation. Thank you

[@vikas-gupta]

Thank you so much 🙏🏼🙏🏼🙏🏼🙏🏼 please keep up the good work....🙏🏼🙏🏼

[@muhammadzubayerhossain78]

Amazing and really helpful explanation. I am truely grateful to her. I study at UCL studying Economics first year and being a student from a top university I have failed to grasp the proper concept of quasi concavity until i stumbled against her video. I highly recommend jalnidh kaur to make more videos of mathematics for Economics . Thank u very much.

[@kavehhhsn]

Thank you so much for the great explanation. Something that I struggled to understand is very clear now.

[@HeavenlyGodlyAngelic]

It's been 10 years but it's helping me now in 2024

[@tubby6007]

even though the video quality is bad your explanation is exceptionally good ,i subscribed to your channel.

[@csd3188]

I had a real trouble understanding the concept. Your explanation is the best! Thank you so much

[@arsh286]

one of the greatest teachers I have ever come across

[@Simbwhaha]

She explains so clear, and straight to the point! Amazing teacher, thumps up

[@kamiladamczewski9860]

Beautifully explained. More videos like that, please.

[@shehaniwanniarachchi2808]

Thank you very much for adding this video. It really helped me to get an idea about these concepts. Wish all the very best to this amazing presenter who expressed the details more clearly with inner enthusiasm.

[@y.a.8480]

searched a lot and thats definitely the best explanation of every video ive watched. Thanks a lot!!

[@akanshagrewal4348]

This really helped a lot!...ma'am would you please make more of such videos on the mathematical concepts of economics...very few such videos are available online and also since it's quarantine time that would really help a lot...

[@ppreeti1601]

Great explanation.... Calm voice and explanation was so good that I got it in one go... 💜thanks a lot

[@olgashanks2922]

Thank you for the video. The explanation is very clear! I had one reservation though, in your quasi-concave examples, shouldn't the definition apply for all x and y, so that if you picked two points on the opposite sides of a "dip" in the curve, you would violate quasi-concavity?

[@nadiaperez-goytia6943]

If I pass my calculus course, it will be because of you. Thank you so much!

[@nathaliehuizeling7799]

I struggled with this, but it is so much clearer now. Thank you!

[@karmantan]

Hi Jalnidh. Thanks for making this video! I was really lost in class today but now I understand this topic!

[@Shivani_Eco]

You explained exceptionally vey well.mam...requesting u to upload more videos.. regarding econometrics..

[@hamza3065]

Couldn't grasp the idea after alot of reading, you made it very clear, thanks alot

[@JivyanshMittal0402]

The way of explanation is a gem!! Thanks a lot ma’am

[@EconomistYT]

Thank you, you saved my 4 marks in ISI Entrance Examination

[@lucassoares6972]

Que didática maravilhosa! Ela passa por todos os meus processos de absorção de matemática. Parabéns! Greetings from Brazil!

[@Aazfar86]

Thanks for saving my life. Much respect.

[@율무차-s6p]

Thank you so much! This video helps me to understand the most difficult part!

[@____darrah____]

Great video! Way better explanation than my micro teacher.

[@anverHisham]

Excellent explanation, very easy to understand... Thanks a lot :)

[@ayeshaahmed3407]

This is super helpful! Why did you stop making videos?

[@choionjung5125]

Thank you so much.. This video is the best among the videos regarding quasi concavity..

[@labhisha1658]

Pretty helpful. Also really clear and I could understand each and every word. Thanks for explaining such a vague concept with so much ease! ❤

[@gunitsingh7206]

for quasiconcavity, should the upper contour sets also shrink as we go on increasing the height?

[@oanphong61]

Your explanation is amazing!

[@alexandrosstefanou830]

The last examples at 08:00 are wrong. The definition must hold for ANY x, y picked from the domain of the function. Thus if we pick a different x,y the image of the points between x,y must be above/below the min/max to be quasiconcave/quasiconvex. Overall, thank you for the intuition.

[@jalnidhify]

Thank you for the feedback. These have been removed.

[@mountainmoss6391]

Splendid explanation! Thanks and keep it going!

[@sakshiaggarwal1915]

Your concepts are crystal clear and the best part is that you know the most difficult part too, to present it. Thank you so very much! It was indeed helpful. I was like mjhe pehle q nhi mila ye video. I literally threw out WOW out of my mouth and was amazed to see the channel's name. Wish you all the very best in life! 😄❤

[@sami-samim]

Such a sweet explanation. Thank you!

[@angshumanrgoswami5524]

Just a note: That combination can be termed as convex combination instead of linear Combination. Reason: you have considered lambda in between 0 and 1.

[@rubenvaneupen7327]

two questions: 1) In the example of the Pear, or the typical 'Mountain', aren't the lower contour sets also convex, just as the upper contour sets? 2) If I understand correctly, you only have to look at the shape of the contour set, and not at the set of any points above a certain level? Cuz in the latter case, e.g., the imploded mountain with 'exponential' slopes, one can connect two point on the slope that fall outside of the shape itself, but it is still said to by quasiconcave cuz one only looks at the contours I guess?

[@arbitrage3736]

Ma'am your explanations are great.I just loved them. Could you please explain us level curve?

[@가환-x9n]

You are a great teacher. Thank you so much

[@toasterwaterable]

Convex functions are interesting because they have exactly one minimum. This makes minimization a straight forward procedure. If you find a minimum, you know it's the global minimum. This contrasts more general functions that may have many local minima, which makes it much more difficult (often practically impossible) to determine when you've found the global minimum. Quasi-convex functions are interesting for the exact same reason - they have exactly one minimum. A quasi-convex function may have many inflection points, meaning it can be convex some places and concave in others. However, because it has exactly one minimum, a quasi-convex function is just as easy to minimize as a purely convex function. For the following reasons, I think that you should either take this video down, or cut out the portion in which you mischaracterize quasi-convexity (and perhaps rerecord a correct version). Your erroneous explanation of quasi-convexity misses the point entirely. By drawing functions with several obvious optima and claiming that they are quasi-convex, you are doing a disservice to yourself and to your viewers. A viewer who understands the concept will probably conclude that you are incompetent. A viewer who doesn't understand the concept will now wrongly believe that they do. Further, you have credited your teacher with your vivid (mis)understanding. I do see that you've acknowledged the errors in the description, but others may not notice, and even if they do, it probably won't help clarify just how wrong your explanation is.

[@GabrialErismann]

+toasterwaterable I agree with you, but is the rest not correct?

[@KK-xb1zj]

I think you have confused pseudo convexity with quasi convexity.🤔

[@kamalchaturvedi2338]

Thanks a lot for this. Finally got this concept sorted in my head :)

[@chintooification]

Very neatly presented video. Thank you!

[@anniecons1985]

Thanks very much!!!!! You're my favorite TA!!!!!!

[@akrishnaprasanth1338]

Could someone explain why x^2 + y^2 = f(x,y) is not a quasi concave utility function, when it is concave, atleast in the first quadrant(which is the quadrant in which we measure utility)?

[@gabiisme]

This video was great. Maybe work on the quality of the camera, because sometimes I couldn't see the writings on the whiteboard. But your explanations were great. You should become a teacher!!

[@TheBaracudabara]

Clear explanation. This is what i was looking for thank you very much

[@zahrajehanzeb3808]

marvelous explanation!

[@reajulchowdhury8534]

You are simply awesome!!! Please upload more videos on other topics as well..

[@arminbolouri8083]

Great explanation! Thank you very much.

[@ammarkamran4908]

Really Good explanation. Will help for my methods of economics class in germany

[@Ferdinaand]

amazing explanation, love her enthusiasm

[@AsmaA-rm9to]

Even it’s an old video and not good quality but your explanations were clear 🙏

[@pramod120895]

Thaks for the clear explanation..really it helped me a lot

[@vaishviigoel7378]

The first diagram that you drew under Quasiconcavity topic, is that Quasiconcave and quasiconvex both? as it was satisfying both min and max condition.

[@razibahmed4833]

Wow. This was a quality explanation. Thank you.

[@ayushigupta2294]

thank you so much mam ... W e need teachers like you in du 👍👍

[@Saurabhyadav-yb2oo]

Ayushi Gupta, 💯 right di , our teachers don't teach so deeply just solve exercise 😂😂

[@HillaryVipond]

Thank you! Very helpful explanation

[@keithchan379]

this video has helped me so much. thank you so much!!! love you

[@ErenErol97]

You are a very clever girl !

[@sisiqiu8216]

the clearest ever! thank you!!

[@AnnisaRatnaSari09]

thankyou. it's really help me. Do you know about pseudoconvex function? If you do, please share video about it. thankyou

[@ΕΙΡΗΝΗΝΟΜΙΚΟΥ-χ6β]

you are amazing honestly. Greetings from Greece

[@jagratigoyal5544]

wonderful explanation

[@alikaraca163]

best explanation ever..

[@suryanshnandwani4892]

hi, would like to know if you also provide some sort of webinars, kindly revert to the comment if this reaches you. thankyou

[@hxi7141]

better explanation given by her than my professor who got his Phd from Princeton: American undergrad education quality is depressing.

[@adreetadas2032]

Thank you! very helpful and clear explanation.

[@amolraswan8717]

I don't that a pear represents a quasi concave function since its level contours will first represent a quasi convex function ( till its lower part resembles a badminton shuttle). from somewhere in the middle of the pear, it will be a quasi concave function. please let me know if my reasoning is correct or not!

[@amolraswan8717]

I meant that from its level contours, it will be clear that it is quasi convex function till its middle portion.

[@anupamathew661]

very good class

[@kriti3011]

Excellent explanation!

[@ベトコン-g5p]

better than many prof. thx

[@ipsitadutta3762]

Very helpful explanation

[@naunidhsingh576]

Nicely presented

[@amashikhasikdar4324]

This is really very helpful.. Thank you so much ❤

[@shivangikhanna2567]

The explanation is very excellent and well taught. However, the constant zooming in and out of the camera is very disturbing. If kept still, it will be better.

[@Iselore]

So a quasiconcave should always be a strictly monotonic function? Since for any f(x) and f(y) in the function, the linear combination of the those points should never lie below the min of the points.

[@hhkchildhood4146]

Iselore A concave function is always quasiconcave. And a concave function need not be monotonic. So that should mean that quasiconcave functions can be non-monotonic. But your point is valid, will think on that and get back to you.

[@hhkchildhood4146]

Jalnidh Kaur Consider an inverse U function - take any x,y and the function value corresponding to any linear combination never slides below the minimum of f(x), f(y) - notice the min of the points changes when you come to the downward sloping stretch. So, monotonicity is not necessary for quasiconcavity. What I think one can generalise for a function in two dimensions is that if a function goes up and then comes down, then it CAN'T go up again. Just like the examples I (mistakenly) showed in the video weren't quasiconcave because they had multiple humps. Does this help?

[@Iselore]

Jalnidh Kaur Yes it helps. I just never thought about a U function. It makes sense to me now. Thank you.

[@yamunasunilkumar4962]

absolutely...quasi an be functions cant take multiple humps... I was thinking about it. it should be either monotonic or concave

[@Minimoose65]

Thank you for this video! It was very helpful!!

[@bilalsadiq5055]

awesome mam,,,,,,,,,,,,,,,,a brilliant explanation

[@carloshjr]

the quality of the video isn't good, but the content of it is excellent

[@hannahhorton1783]

Great video, thanks for your help!

[@lunasong3516]

Thank you so much! This was sooooo helpful!

[@qwertyuiopqwertyuiop5619]

VERY HELPFUL FOR YOUNGER STUDENTS

[@tubby6007]

could you please do a video on level curves,i would be eternally grateful

[@veeshanR]

Thanks for correcting the mistake.

[@tianyangzhang4727]

I like your pear example!

[@МухаметУразбаев]

There some comments to your explanation: 7:49 you drae not exactly quasiconcave function since there possible such x and y wich violate quasiconcavity(you have valleys)

[@jalnidhify]

Thanks for your feedback. The relevant example has been removed.

[@sukirtiranasaria736]

The video was a great help !!

[@kaleyjiang3578]

It's super helpful! Thank you sooo much！

[@econaveenhari]

Is this from Osbrone tutorials?

[@meemee329]

thank you so much..you made my life so easy......

[@AMEYZINGStudios]

This is amazing. Thank you so much!

[@drrahatjafri]

Thanks for sharing this video. it is very helpful

[@vidisha2683]

You are a great teacher.. Thanks :)

[@rtdjin3000]

Your presentation is very nice. Requesting you to please use a better camera, else improve lighting.

[@johnkarippery9919]

what is Pseudoconvexity?

[@cloud-tutorials]

Can you draw contour maps of pear

[@parvanehshafiei1]

Brava! that was so clear explanations, tnx